A Level Bio Spec MOCK

A Level Biology A (Salters-Nuffield) SPECIMEN PAPERS Pearson Edexcel Level 3 Advanced GCE in Biology A (Salters-Nuffield) (9BN0)

Pearson Edexcel Level 3 Advanced Level GCE in Biology A (Salters-Nuffield) (9BN0) Specimen Papers First certification 2016

Contents 1 Introduction

1

2 General marking guidance

3

3 Paper 1: The Natural Environment and Species Survival

5

4 Paper 1 Mark Scheme

41

5 Paper 2: Energy, Exercise and Co-ordination

63


99

7 Paper 3: Pre-release material

121

8 Paper 3: General and Practical Applications in Biology

133


159

References to third party materials are made in these specimen papers are made good faith. Pearson does not endorse, approve or accept responsibility for the content of materials, which may be subject to change, or any opinions expressed therein. (Material may include textbooks, journals, magazines and other publications and websites.) All information in this document is correct at time of publication. All the material in this publication is copyright © Pearson Education Limited 2015

Introduction These specimen papers have been produced to complement the sample assessment materials for Pearson Edexcel Level 3 Advanced GCE in Biology A (Salters-Nuffield) and are designed to provide extra practice for your students. The specimen papers are part of a suite of support materials offered by Pearson. The specimen papers do not form part of the accredited materials for this qualification.

Pearson Edexcel Level 3 Advanced Level GCE in Biology A (Salters-Nuffield) Specimen Papers - Issue 1 - October 2015 © Pearson Education Limited 2015

1

General marking guidance ●

All candidates must receive the same treatment. Examiners must mark the last candidate in exactly the same way as they mark the first.

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Mark schemes should be applied positively. Candidates must be rewarded for what they have shown they can do rather than be penalised for omissions.

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Examiners should mark according to the mark scheme – not according to their perception of where the grade boundaries may lie.

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All the marks on the mark scheme are designed to be awarded. Examiners should always award full marks if deserved, i.e. if the answer matches the mark scheme. Examiners should also be prepared to award zero marks if the candidate’s response is not worthy of credit according to the mark scheme.

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Where some judgement is required, mark schemes will provide the principles by which marks will be awarded and exemplification/indicative content will not be exhaustive.

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Brackets around parts of words / phrases in this mark scheme indicate the possible additional words / phrases candidates may write as their answer. They must not be awarded twice for an answer relating to one bullet point.

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Where a word is underlined, that word must be included in the answer to be awarded a mark for that point.

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When examiners are in doubt regarding the application of the mark scheme to a candidate’s response, a senior examiner must be consulted before a mark is given.

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Crossed-out work should be marked unless the candidate has replaced it with an alternative response.


2

3

Write your name here Surname

Pearson Edexcel Level 3 GCE

Other names

Centre Number

Candidate Number

Biology A (Salters Nuffield)

Advanced Paper 1: The Natural Environment and Species Survival Specimen Paper for first teaching September 2015

Time: 2 hours

Paper Reference

9BN0/01

You may need a ruler, a pencil and a calculator.

Total Marks

Instructions

Use black ink or ball-point pen. • Fill boxes at the top of this page with your name, • centrein the number and candidate number. Answer • Show yourall questions. in any calculation questions and include units in your • answer whereworking appropriate. the questions in the spaces provided • A– nswer there may be more space than you need. may use a scientific calculator. • You marked with an asterisk (*), marks will be awarded for your ability • toIn questions structure your answer logically, showing how the points that you make are related or follow on from each other where appropriate.

Information

total mark for this paper is 100. • The for each question are shown in brackets • –Theusemarks this as a guide as to how much time to spend on each question.

Advice

each question carefully before you start to answer it. • Read to answer every question. • Try • Check your answers if you have time at the end.

Turn over

S49421A ©2015 Pearson Education Ltd.

3/2/3/


3

Answer ALL questions. Write your answers in the spaces provided. Some questions must be answered with a cross in a box . If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . 1 Many animals reproduce sexually. The diagram shows a healthy human sperm cell.

Q

S

P

Magnification ´4000

R

(a) (i) In which part of the sperm cell are the mitochondria located?

(1)

A P B Q C R D S (ii) Which of the following is the approximate diameter of the sperm cell nucleus?

(1)

A 0.4 μm B 4 μm C 0.4 nm D 4 nm (iii) Which of the following describes the chromosome number in this human sperm cell? (1) A diploid B haploid C polyploid D tetraploid


4

(b) Explain why a defective acrosome reaction may result in male infertility.

(4)

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(c) Males produce large numbers of sperm cells each with a different genotype.

Describe how the variation in sperm cell genotype arises.

(3)

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(Total for Question 1 = 10 marks)

Turn over Pearson Edexcel Level 3 Advanced Level GCE in Biology A (Salters-Nuffield) Specimen Papers - Issue 1 - October 2015 © Pearson Education Limited 2015

5

2 The movement of materials into and out of a cell needs to be controlled.

(a) Describe what is meant by the term fluid mosaic with reference to cell membranes. (2)

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(b) Goblet cells lining the bronchi produce mucus. This mucus is released by exocytosis.

(i) Explain how goblet cells release mucus by exocytosis.

(2)

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(ii) The consistency of the mucus is determined by the movement of water, by osmosis, from the cells lining the bronchi.

Explain how the partial permeability of the surface membrane of the cells lining the bronchi allows osmosis to take place.

(2)

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6

(iii) Describe how thicker mucus would affect gas exchange across the walls of the alveoli. (2)

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7

3 Photosynthesis is the process by which plants fix carbon.

(a) The diagram shows some of the light dependent reactions of photosynthesis. NADP NADPH PSII 2e–

Y

PSI

X H2O

(i) Complete the box with the products of the reaction at PSII.

(ii) Which of the following is the type of reaction taking place at X?

(1) (1)

A condensation B hydrolysis C photolysis D reduction

(iii) Which of the following molecules are found in the PSI and PSII?

(1)

A ATP B ATP synthase C chlorophyll D RUBISCO

(iv) In which part of the chloroplast does the reduction of NADP take place?

(1)

A chloroplast outer membrane B chloroplast stroma C granum D thylakoid lumen


8

(v) Describe the role of the group of membrane proteins represented by Y in the diagram.

(2)

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9

(b) Wheat and maize are used as biofuel crops.

Scientists have investigated the effect of incident radiation and leaf nitrogen concentration on the growth of wheat and maize.

Incident radiation is a measure of the useful light energy hitting the plant. Leaf nitrogen concentration is a measure of the availability of nitrogen in the soil.

The results of these investigations are shown in the graphs.

Above ground dry mass / g m–2

3000 – Key Maize Wheat

2500 – 2000 – 1500 – 1000 – 500 – 0– 0

200

400

600

Cumulative incident radiation / MJ m–2

18 – Key

16 –

Maize Wheat

Carbon fixed / mg m–2 s–1

14 – 12 – 10 – 8– 6– 4– 2– 0– 0

50

100

150

Leaf nitrogen concentration / au


10

(i) Scientists calculated the dry mass produced per MJ of incident radiation for wheat. This is shown in the table. Plant

Above ground dry mass / g MJ-1

Wheat

3.25

Calculate the above ground dry mass produced per MJ of incident radiation for maize.

(2)

Answer ........................................ . . . . . . . . . . . . . . . . . . . g MJ–1 (ii) Analyse the information provided about maize and wheat to determine which crop should be used for the production of biofuels.

(2)

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11

(iii) Sugar cane crops are also being grown for the production of biofuel.

Devise an experiment to investigate the effect of light intensity on the above ground dry mass of sugar cane crops grown in a field.

(5)

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12

4 Lysozyme is one component of the non-specific response to infection.

(a) Describe what is meant by a non-specific response to infection.

(3)

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13

(b) A student investigated the activity of lysozyme in tears.

A suspension of bacteria was mixed with molten agar and poured into a Petri dish. After the agar had solidified, wells were cut and different dilutions of tear sample were placed in the wells.

After 24 hours the Petri dish was inspected.

1 8

1 4 Control

Undiluted

Well 1 2 Bacterial growth

Clear zone Tear samples

24 hours later

(i) State the relationship between lysozyme dilution and the size of the clear zone.

(1)

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(ii) Calculate the area of the clear zone for the undiluted tear sample.

(Area of a circle = πr2)


(2)

14

(c) Explain how the student could adapt the investigation to study the effect of pH on the activity of lysozyme.

(3)

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15

5 Madagascar is an island rich in biodiversity.

Lemurs are a diverse group of primates endemic to Madagascar.

Scientist suggest there may be as many as 100 different species of lemur.

(a) (i) State what is meant by the term endemic.

(1)

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(ii) Describe what is meant by biodiversity.

(2)

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(iii) Explain how the biodiversity of lemurs in two different parts of Madagascar could be compared.

(3)

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16

(b) One species of lemur, the Aye-aye, is found throughout the forests of Northern Madagascar.

Deforestation is taking place in this part of Madagascar.

Scientists have identified three separate populations of Aye-aye in this area, as shown on the map.

Location of the three populations of Aye-aye in Northern Madagascar

Explain how these three populations could become distinct species.

(3)

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17

6 Ebola haemorrhagic fever is a life-threatening disease caused by the Ebola virus. (a) Explain why antibiotics are not used to treat Ebola haemorrhagic fever.

(2)

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(b) Some of the blood plasma of individuals who have survived infection with Ebola can be collected. This can be used in the treatment of individuals currently infected with Ebola. Explain why the blood plasma from survivors can be used to treat new cases of Ebola infection. (3) ................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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18

(c) A study of the 2014 Ebola outbreak in Sierra Leone found that the Ebola virus was evolving rapidly.

Explain why the evolution of the virus might reduce the effectiveness of any vaccine being developed.

(4)

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19

7 Tissues of the human body have different stem cell populations.

These stem cells divide to replace and renew cells in these tissues.

(a) Describe the properties of a stem cell.

(2)

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(b) Scientists have observed a relationship between the number of times a stem cell population divides in a tissue and the risk of developing cancer in that tissue.

This relationship is shown in the graph. 1

Risk of developing cancer

Basal cell 0.1

Lung (smokers)

Colon Leukaemia

0.01

Liver Oesophagus

0.001

Lung (non-smokers)

Bone

0.0001 106

107

108

109

1010

1011

1012

1013

Number of stem cell divisions in an individual’s lifetime


20

(i) The correlation coefficient for the data is 0.937. The table shows some critical values for this correlation coefficient. Critical values for the correlation coefficient n

p = 0.05

4

1.00

5

0.90

6

0.83

7

0.71

8

0.64

9

0.60

10

0.56

Which of the following correctly describes the correlation?

(1)

A non-significant and positive B non-significant and negative C significant and positive D significant and negative (ii) Explain the relationship between the number of stem cell divisions and the risk of developing cancer.

(2)

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21

(iii) The graph shows that the risk of developing lung cancer is greater in a cigarette smoker compared to a non-smoker. Calculate how many times greater.

(2)

Answer .............................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (iv) Explain why cigarette smokers have a higher risk of developing lung cancer than non-smokers. (2) ................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



22

8 Crustose coralline algae are a group of photosynthetic red algae that play an important role in the formation of coral reefs.

These algae deposit calcium carbonate in their cell walls to form encrusting and rock-like structures.

(a) (i) Write an expression that describes net productivity.

(1)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) The graph shows net productivity and respiration for one species of crustose coralline algae found at different water depths.

Production and consumption of organic carbon / g C m–2 day–1

2.5 –

2.0 –

1.5 –

1.0 –

Key

0.5 –

Respiration Net productivity 0– 0

5

10

15

20

Water depth / m

On the graph, plot the gross productivity for this species.

(1)


23

(iii) Analyse the data to explain the effect of water depth on net productivity.

(3)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

*(b) Scientists investigated the effect of water temperature and carbon dioxide concentration on the growth of one species of crustose coralline algae. The growth was measured by recording the percentage cover of the algae on a surface. The results of this investigation are shown in the table. Growth conditions

Percentage cover (%)

Temperature / °C

CO2 concentration / ppm

17

400

100

17

700

70

20

400

100

20

700

35

The normal temperature and carbon dioxide concentration in the natural habitat of this species are 17°C and 400 ppm CO2.


24

Analyse the data in the graph and the table to assess the possible impact of the continued burning of fossil fuels on crustose coralline algae.

(6)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



25

9 Liver cells synthesise and export a variety of proteins. (a) The image is a transmission electron micrograph of part of a liver cell.

M N

L K

500 nm (i) Which of the following structures is involved in respiration?

(1)

A K B L C M D N (ii) Which of the following structures is involved in synthesising lipids?

(1)

A K B L C M D N


26

(iii) The site of synthesis of proteins to be released by exocytosis is

(1)

A K B L C M D N (iv) Calculate the maximum width of the structure labelled K.

(2)

Maximum length ............................ . . . . . . . . . . . . . . . . . . . . . . . . . . . nm (b) Collagen is a fibrous protein. Explain how the structure of collagen is related to its function.

(4)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


27

(c) Fibrosis of the liver is a chronic condition that can lead to cirrhosis of the liver and liver failure. In fibrosis of the liver, liver cells secrete excess collagen. There is an association between fibrosis of the liver and alcohol consumption in humans. Scientists have investigated the effects of alcohol intake on collagen synthesis in rats. The results are shown in the table.

Alcohol intake / week

Synthesis of collagen in the liver / au

none

14

small volume each day

16

one large volume on day one

19

one large volume on day one and a small volume from day two and day seven

27

(i) Deduce the effect of alcohol intake on fibrosis of the liver in rats.

(3)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


28

(ii) The scientists have suggested that epigenetic events are involved in regulating collagen synthesis in rats given alcohol.

Explain how epigenetic events might be involved in regulating collagen synthesis in rats given alcohol.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



29

10 Common variable immunodeficiency (CVID) is one of the most commonly diagnosed immunodeficiency disorders. The infection history of a group of individuals with CVID is summarised in the table.

Type of infection

Characteristics of infection Frequency of infection

Severity of infection

Bacterial

Much more frequent than expected

Effects of infection are more serious than in the general population

Viral

Slightly higher frequency than expected

Effects of infection are comparable to infection in the general population

Concentration of antibody against pneumococcal antigens

The average antibody response of two groups, following immunisation with a bacterial pneumococcal vaccine, is shown in the graph.

without CVID

with CVID

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Time / days


30

The distribution of lymphocytes in the blood for the two groups is shown in the table.

B lymphocytes

T lymphocytes

T helper cell : T killer cell ratio

With CVID

8

78

1.7 : 1

Without CVID

14

80

1.5 : 1

Group

Percentage of white blood cells (%)

Analyse the data to evaluate how the immunological defect in the group with CVID might be treated.

(6)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Total for Question 10 = 6 marks) TOTAL FOR PAPER = 100 MARKS


31

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Every effort has been made to contact copyright holders to obtain their permission for the use of copyright material. Pearson Education Ltd. will, if notified, be happy to rectify any errors or omissions and include any such rectifications in future editions


34

Acceptable Answer

Answer

Answer

the {egg / oocyte} membrane is protected by the zona pellucida (and follicle cells)

(if acrosome reaction defective) enzyme not released

{ digestive enzymes / acrosin } will not break down the zona pellucida

sperm will not be able to { fuse with the oocyte membrane / fertilise the oocyte }









An explanation that makes reference to the following:

B (haploid)

B (4 μm)

B (Q)

Answer


Question Number 1(b)

Question Number 1(a)(iii)

Question Number 1(a)(ii)

Question Number 1(a)(i)

Biology A (Salters-Nuffield) Advanced Paper 1 (9BN0/01)

(1)

(1)

(1)

(1)

Allow egg cell for oocyte

Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

(4)

Mark

(1)

Mark

(1)

Mark

(1)

Mark

35

variation is produced in meiosis

as a result of { crossing over / recombination } of alleles between chromatids

the independent assortment of chromosomes







A description that makes reference to the following:

Acceptable Answer


Question Number 1(c)

(1)

(1)

(1)

(3)

Mark

36

Total for Question 1 = 10 Marks

Additional Guidance

mosaic refers to the random association of proteins (of different shapes and sizes) within the membrane



(these vesicles) fuse with the cell membrane releasing the mucus



partially permeable membrane is a barrier to some solutes but not water

enables a concentration gradient of { solutes / water }






Acceptable Answer

mucus contained in membrane bound vesicles inside the cell




Acceptable Answer

fluid refers to the movement of the phospholipids in the plane of the membrane




Acceptable Answer


Question Number 2(b)(ii)

Question Number 2(b)(i)

Question Number 2(a)

(1)

(1)

(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

Additional Guidance

(2)

Mark

(2)

Mark

(2)

Mark

37

increased diffusion distance / decreased surface area

reduced (rate of) gas exchange






Acceptable Answer


Question Number 2(b)(iii)

(1)

(1) (2)

Mark

38

Total for Question 2 = 8 marks

Additional Guidance

Acceptable Answer

Answer

Answer

Answer

electron transport

movement of hydrogen ions across thylakoid membrane

ATP production / photophosphorylation







A description that makes reference to two of the following:

B (chloroplast stroma)

C (chlorophyll)

C (photolysis)

2H+ + ½O2

Acceptable Answer


Question Number 3(a)(v)

Question Number 3(a)(iv)




(1)

(1)

(1)

Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

Allow ‘hydrogen ions’, ‘protons’ and ‘oxygen’

Additional Guidance

(2)

Mark

(1)

Mark

(1)

Mark

(1)

Mark

(1)

Mark

39

correct answer 4.5



maize produce more above ground dry mass for a particular amount of incident radiation

maize fix more carbon for a particular leaf nitrogen concentration

maize will grow in less optimum conditions so better for biofuel production







An answer that makes reference to two of the following:

Acceptable Answer

appropriate x and y axis values identified



Acceptable Answer




(1)

(1)

(1)

Additional Guidance

Allow full marks for correct answer with no working

(1) = 4.5

Example of Calculation: (1) (1800 – 900) ÷ 200

Additional Guidance

(2)

Mark

(2)

Mark

40

{ select / plant } a field of sugar cane

sample, at suitable time intervals, using randomly placed quadrats

measure light intensity

harvest, dry and weigh sugar cane

{ monitor / record } other abiotic factors











An answer that makes reference to the following:

Acceptable Answer



(1)

(1)

(1)

(1)

(1)

(5)

Mark

41


Additional Guidance


(1) Example of Calculation 3.14 × 72 = 154 mm2

• correct answer

Additional Guidance

Additional Guidance

(1) 14 mm

Acceptable Answer

(1)

(1)

(1)

Additional Guidance

• correct diameter or radius measured

positive correlation

does not react to specific antigens





does not involve recognition of infectious agent



Acceptable Answer

response that is effective against (wide) range of infectious agents




Acceptable Answer





(2)

Mark

(1)

Mark

(3)

Mark

42

use of buffers of different pH

control other variables e.g. temperature

{ compare / measure } diameter of clear zone








Acceptable Answer



(1)

(1)

(1)

(3)

Mark

43


Additional Guidance

Acceptable Answer

species found only in one geographical location

the variety of alleles in a { gene pool / population / species }



record the number of species of lemur and the number of individuals of each species

calculate the diversity index (for each location)

so the higher the index, the greater the biodiversity

DNA profiling / gel electrophoresis / molecular phylogeny / proteomics









An explanation that makes reference to three of the following:

Acceptable Answer

the variety of species (in an ecosystem / community / habitat)






Acceptable Answer





(1)

(1)

(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

Additional Guidance

(3)

Mark

(2)

Mark

(1)

Mark

44

deforestation results in (geographical) isolation of the populations of Aye-ayes

resulting in reduced gene flow between the populations

different selection pressures leading to natural selection

leading to sympatric speciation










Acceptable Answer



(1)

(1)

(1)

(1)

(3)

Mark

45


Additional Guidance

viruses therefore unaffected by antibiotics



antibodies given to individuals infected with Ebola will provide passive immunity

the antibodies provided will therefore { agglutinate / opsonise } the virus particles





results in a change in the shape of the viral proteins

therefore antibodies can no longer bind to the virus





(1)

Mark

(3)

Mark

(2)

Mark

46

(4) Total for Question 6 = 9 marks

(1) Ebola is an RNA virus but allow reference to mutations in DNA (1)

mutations in the virus nucleic acid



Additional Guidance

Additional Guidance

vaccine stimulates immune response to make antibodies (1) Accept reference to antigens specific to viral proteins

(1)

(1)

(1)

(1)

(1)

Additional Guidance




Acceptable Answer

survivors will have antibodies specific to the virus in their plasma




Acceptable Answer

antibiotics target { organelles / structures / processes } found in bacteria




Acceptable Answer





more mutations result in greater chance of cancer



correct risks identified

correct calculation





Acceptable Answer

greater number of cell divisions means more opportunities for errors in DNA replication




Acceptable Answer

C (significant and positive)

has the potential to give rise to specialised cells



Answer

a cell that can continue to divide




Acceptable Answer






Additional Guidance

Additional Guidance

Additional Guidance


(1) Example of calculation: 0.08 ÷ 0.004 = 20.0

(1) 0.08 and 0.004

(1)

(1)

(1)

(1) Allow ‘no Hayflick limit’

Additional Guidance

(2)

Mark

(2)

Mark

(1)

Mark

(2)

Mark

47

cigarettes { are an environmental risk factor / contain carcinogens }

that increases the number of mutations in cells

resulting in uncontrolled cell division







An explanation that makes reference to two of the following:

Acceptable Answer


Question Number 7(b)(iv)

(2)

Mark

48


(1) Accept description of how mutations arise (1)

(1)

Additional Guidance

Acceptable Answer

there will be a large decrease in net productivity as depth increases

(due to) large decrease in gross productivity as depth increases

lower light intensity results in less photosynthesis

and (only a) small decrease (in utilisation of carbon) in respiration as depth increases










correctly plotted value

Acceptable Answer

(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

Allow NPP = GPP - R

Additional Guidance

2.3 at 0 1.4 at 6 0.9 at 18

net (primary) productivity = gross (primary) productivity - respiration

Acceptable Answer





(3)

Mark

(1)

Mark

(1)

Mark

49

Indicative content

5-6

3-4

1-2

Mark Marks

50

The answer shows a well-developed and sustained line of scientific reasoning which is clear and logically structured.

The answer shows some linkages and lines of scientific reasoning with some structure. An answer is made which is supported throughout by sustained application of relevant evidence of analysis, interpretation and/or evaluation of both pieces of scientific information.

The answer will contain basic information with some attempt made to link knowledge and understanding to the given context. An answer will be given with occasional evidence of analysis, interpretation and/or evaluation of both pieces of scientific information.

Descriptor No awardable content An answer may be attempted but with limited interpretation or analysis of the scientific information with a focus on mainly just one piece of scientific information.

The indicative content below is not prescriptive and candidates are not required to include all the material which is indicated as relevant. Additional content included in the response must be scientific and relevant.  burning fossil fuels increases atmospheric concentrations of CO2, a greenhouse gas leading to rising sea levels, increased surface temperatures and increased CO2 concentration in oceans  small changes in sea level have limited effect on the crustose coralline algae  algae are adversely affected by increased carbon dioxide concentrations  there is a greater effect of increased carbon dioxide at higher temperatures  continued burning of fossil fuels may reduce productivity of crustose coralline algae  reefs will grow more slowly, become more susceptible to damage resulting in loss of habitat

Answers will be credited according to candidate's deployment of knowledge and understanding of the material in relation to the qualities and skills outlined in the generic mark scheme.


3

2

1

Level Level 0

Question Number *8(b)

measures width on diagram

correct answer



Acceptable Answer

Acceptable Answer

Acceptable Answer



D (N)

C (M)

A (K)

Answer







(1) = 940 nm

Example of calculation (1) (500 x width of K) ÷ length of bar

Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

(2)

Mark

(1)

Mark

(1)

Mark

(1)

Mark

51

chains are held together by { hydrogen bonding / covalent cross links }

flexible without stretching (due to triple helix)

chains of collagen associate together to form fibrils

(fibrils) have a high tensile strength (and function to support tissues)









combined intake has greatest effect

a greater level of collagen indicates a greater amount of fibrosis







therefore the higher the alcohol intake the greater the level of fibrosis

AND

alcohol intake increases collagen synthesis



An answer that makes reference to any two of the following:

Acceptable Answer

(1)

due to every third amino acid { being glycine / having a small R group }



(1)

(1)

(1)

(1)

(1)

(1)

(1)

(1)

(1)

 three { polypeptide / collagen } chains tightly coiled around each other

An explanation that makes reference to four of the following:

Acceptable Answer


Question Number 9(c)(i)


Additional Guidance

Additional Guidance

(3)

Mark

(4)

Mark

52

exposure to alcohol may result in { changes of methylation of DNA / modification of histones }

so that the collagen gene is more likely to be { activated / expressed / transcribed }






Acceptable Answer


Question Number 9(c)(ii)

(1) (2)

Mark

53


(1) Allow reference to other correct epigenetic modifications

Additional Guidance

Indicative content

5-6

3-4

1-2

Mark 0

        

54

A conclusion is made, demonstrating sustained linkages to biological knowledge and understanding with evidence to support the judgement being made. Total for Question 10 = 6 marks

A conclusion is made, demonstrating linkages to elements of biological knowledge and understanding, with occasional evidence to support the judgement being made. A scientific judgement is made which is supported throughout by sustained application of relevant evidence from the analysis and interpretation of the scientific information.

A conclusion may be attempted, demonstrating isolated elements of biological knowledge and understanding but with limited evidence to support the judgement being made. A scientific judgement is made through the application of relevant evidence, with strengths and weaknesses of each method identified.

Descriptor No awardable content Limited scientific judgement made with a focus on mainly just one method, with a few strengths/weaknesses identified.

the CVID group is more susceptible to bacterial infections the CVID group produces fewer antibodies to bacterial antigens have a reduced percentage of B cells have a similar ratio of T helper to T killer cells have a normal percentage of T lymphocytes can defend themselves against viruses but not bacteria (therefore) antiviral medication not required could prescribe (prophylactic) antibiotics could provide passive immunity by giving them antibodies / immunoglobulins

The indicative content below is not prescriptive and candidates are not required to include all the material which is indicated as relevant. Additional content included in the response must be scientific and relevant.



3

2

1

Level 0

Question Number *10



Other names

Centre Number

Candidate Number

Biology A (Salters Nuffield)

Advanced Paper 2: Energy, Exercise and Co-ordination

Specimen Paper for first teaching September 2015

Time: 1 hour 30 minutes

Paper Reference

9BN0/02

You do not need any other materials.

Total Marks

Instructions

Use black ink or ball-point pen. • Fill boxes at the top of this page with your name, • centrein the number and candidate number. Answer • Answer allthequestions. in the spaces provided • – there may bequestions more space than you need. You may use a scientific calculator. • Questions labelled with asterisk (*) are ones where the quality of your written • communication will be assessed – you should take particular care with your spelling, punctuation and grammar, as well as the clarity of expression, on these questions.

Information

total mark for this paper is 100. • The for each question are shown in brackets • –Theusemarks this as a guide as to how much time to spend on each question.

Advice

each question carefully before you start to answer it. • Read Try to every question. • Checkanswer • your answers if you have time at the end. Turn over


3/3/3/


55

Answer ALL questions. Write your answers in the spaces provided. Some questions must be answered with a cross in a box . If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . 1 Movement of the arm at the elbow joint results from the contraction of muscles. The diagram shows some of the structures in a human arm.

F

E G

(a) Give the term for a pair of muscles that brings about movement at a joint.

(1)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) (i) Give a reason why F can be described as a flexor muscle.

(1)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Describe how G interacts with E to enable movement at this joint.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


56

(c) (i) Muscle contains actin and myosin protein fibres. Which of the following describes the primary structure of a protein?

(1)

A amino acids joined by hydrogen bonds B amino acids joined by ester bonds C amino acids joined by peptide bonds D amino acids joined by phosphodiester bonds (ii) Describe the structure of an amino acid.

(3)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



57

2 The diagram shows part of the membrane of the outer segment of a rod cell.

          

L

{

M

N (a) Which of the following is the part labelled L?

(1)

A fatty acid tail B phosphate head C phospholipid D phospholipid bilayer (b) (i) Give the name of the visual pigment labelled M.

(1)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Give the name of the light-absorbing part of the visual pigment labelled N.

(1)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


58

(c) Describe how the absorption of light by the part labelled N results in an action potential in the optic nerve.

(3)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



59

3 There are many factors that affect the development of cardiovascular disease.

The table contains information about four different patients. Patient

Gender

Age

Systolic blood pressure / mm Hg

HDL: Total cholesterol

E

Female

49

120

60 :160

F

Female

67

150

60 :140

G

Male

51

170

30 :180

H

Male

67

140

60 :140

(a) (i) Which two of these patients are at the greatest risk of developing cardiovascular disease?

(1)

A E and F B F and G C G and H D H and E

(ii) Explain why these two patients have the greatest risk of developing cardiovascular disease.

(4)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


60

(b) Electrocardiograms can aid the diagnosis of heart conditions.

A doctor recorded the following electrocardiogram for a patient with a healthy heart.

R T

P Q

S

(i) State what is measured along the x‑axis and y‑axis of this electrocardiogram.

(1)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Which part of an electrocardiogram indicates the depolarisation of the atria?

(1)

A P B Q C R D S

(iii) Which part of the electrocardiogram indicates when the atrioventricular valves would close?

A P to Q

(1)

B Q to R C S to T D T to P


61

(c) The doctor recorded this electrocardiogram for another patient.

Explain why the electrocardiogram indicates that this patient has a heart condition. (2) ................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


62

(d) Another factor that is associated with an increased risk of heart disease is the use of antidepressant drugs. There are a number of drugs available for treating depression. The graph shows some of the side effects of one of these drugs. 60 Number of patients

50 40 30 20

Dizziness

Nausea

Fatigue

Insomnia

Dry mouth

Sleepiness

0

Weight gain

10

Side effects of drug Explain why the side effects of this antidepressant drug could increase the risk of developing heart disease.

(4)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



63

4 The maintenance of blood glucose levels is an example of homeostasis. (a) State what is meant by the term homeostasis.

(1)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) People with type 1 diabetes have to inject insulin to control their blood glucose levels. Blood glucose levels are normally maintained between 4 and 8 mmol dm–3. The graph shows the changes in blood glucose over the course of two days for a person with diabetes being treated with insulin.

Blood glucose / mmol dm–3

15

10

5

0

08 12 16 20 24 04 08 12 16 20 24 04 08 Time of day

If insulin is injected and a meal is missed, blood glucose levels may fall too low. Calculate the change in mass of glucose in 1 dm-3 of blood between 10:00 h and 17:00 h on Day 2. A blood glucose level of 4 mmol dm-3 is equivalent to 72 mg 100 cm-3.

(3)

Answer .............................. . . . . . . . . . . . . . . . . . . . . . . . . . . mg


64

(c) Glucagon is a hormone that is usually released when the level of blood glucose falls too low. Glucagon stimulates the liver to break down glycogen into glucose. (i) Which of the following processes breaks down glycogen into glucose?

(1)

A condensation hydrolysis B C methylation D phosphorylation (ii) Which arrangement shows the structure of the bond that is broken in this process? O A C

O

C

C B

O

C

(1)

H C C

N

C O

D C

O

P

O

C

O


65

(d) Some people have a disorder that reduces their ability to produce an enzyme required to break down glycogen. This enzyme is glycogen phosphorylase.

The symptoms of this disorder include muscle weakness and lack of stamina when exercising.

(i) Explain why a low concentration of this enzyme would cause the symptoms described.

(3)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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(ii) Devise an experiment to investigate the effect of glycogen phosphorylase concentration on the breakdown of glycogen.

(3)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



66

5 Mitochondria are organelles found in eukaryotic cells. The diagram shows a mitochondrion. ribosome matrix DNA inner membrane outer membrane (a) Where in the mitrochondrion does the Krebs cycle take place?

(1)

A inner membrane B matrix C outer membrane D ribosome (b) Compare and contrast the structure of a prokaryotic with that of a mitochondrion, as shown in the diagram.

(3)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


67

(c) Mitochondrial diseases are caused by mutations in the DNA of the mitochondria. One type of mitochondrial disease is caused by the production of defective ATP synthase. (i) Explain how a mutation in the mitochondrial DNA could result in defective ATP synthase being produced.

(3)

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(ii) Mitochondrial myopathy is a mitochondrial disease. The symptoms of this disease vary in severity. The table shows the relationship between the percentage of mitochondria with mutated DNA in parents and the severity of the symptoms in their child. Percentage of mitochondria with mutated DNA in the mother (%)

Percentage of mitochondria with mutated DNA in the father (%) 0

20

50

80

0

No symptoms

No symptoms

No symptoms

No symptoms

20

No symptoms

No symptoms

No symptoms

No symptoms

50

Mild symptoms

Mild symptoms

Mild symptoms

Mild symptoms

80

Severe symptoms

Severe symptoms

Severe symptoms

Severe symptoms


68

Explain the effects that the percentage of mitochondria with mutated DNA in the parents has on the severity of symptoms in their child.

(3)

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69

6 An investigation was carried out to test the effect of temperature on the rate of respiration in germinating seeds. The diagram shows the respirometer that was used to carry out this investigation.

Germinating seeds

Capillary tube (0.7 mm internal diameter) containing coloured oil

Potassium hydroxide solution Tube A

Tube B

(a) (i) Describe the purpose of the potassium hydroxide solution in this respirometer.

(2)

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70

(ii) The level of the coloured oil dropped on the left-hand side by 8.2 mm in 12 minutes. Calculate the rate of respiration of these seeds. Express your answer as volume of oxygen used per minute to two decimal places. (Volume of cylinder = πr 2h )

(3)

Answer ................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *(b) Devise an investigation, using this respirometer, to obtain valid data to show the effect of temperature on the rate of respiration in germinating seeds.

(6)

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71

7 Haemophilia is a genetic disorder where blood does not clot normally. It can be treated by injecting factor VIII, a protein involved in the blood-clotting process that is not produced by people with haemophilia type A. Bacteria can be genetically modified to produce factor VIII. (a) The diagram shows some of the steps involved in genetically modifying bacteria to produce factor VIII. Step 1 Gene coding for factor VIII is removed from the human genome

Step 2 Gene for factor VIII is inserted into a vector

Step 3 Vector is inserted into bacteria

Step 4 Bacteria are grown in large numbers and factor VIII is produced (i) Describe the difference between a gene and the genome

(2)

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72

(ii) Give the name of the type of enzyme that would be used to insert the gene into the DNA of the vector at Step 2.

(1)

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(iii) Give an example of a suitable vector that would be used in Step 2 or 3.

(1)

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(iv) Describe how the genetically modified bacteria would use the gene from the human genome to produced factor VIII in Step 4.

(2)

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73

(b) Factor VIII is required for the activation of prothrombin. Explain why the blood-clotting process does not take place normally when a person with haemophilia type A cuts their hand.

(3)

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74

8 Some marine snails produce chemicals called conotoxins. These chemicals paralyse the prey of these snails by interfering with the conduction of nerve impulses to muscles. Conotoxins can be modified to produce painkillers. The table shows the membrane proteins affected by different conotoxins. Type of conotoxin

Membrane protein affected

Alpha

acetylcholine receptors

Delta

voltage-gated sodium ion channels

Kappa

voltage-gated potassium ion channels

Omega

calcium ion channels

*(a) Analyse the data to explain how conotoxins can interfere with the conduction of nerve impulses to muscles.

(6)

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75

(b) The effects of conotoxins on the nervous system were first demonstrated in experiments involving animals.

These experiments were involved in the development of painkillers from conotoxins.

(i) Describe the ethical issues concerning the use of animals in this research.

(2)

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76

(ii) After testing on animals, painkillers undergo three-phased testing.

In an investigation testing the effectiveness of a painkiller produced from conotoxin, the new painkiller was tested on a group of healthy volunteers.

Explain the reasons for this stage in the testing of the painkiller.

(2)

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77

9 An experiment was carried out to investigate mineral deficiencies on the growth of seedlings. The effects of two mineral deficiencies on two different species of plant were investigated. Test tubes were half filled with an aqueous gel containing a mineral solution without calcium ions. Seeds of rice or fenugreek were placed separately in these test tubes. These test tubes were placed by a window for two weeks to allow the seeds to germinate and the seedlings to grow. This was repeated using test tubes containing mineral solution without magnesium ions. (a) A control should have been used in this investigation. (i) Which of the following would be a suitable control?

(1)

A complete mineral ion solution B distilled water C dry gel D tap water (ii) In this investigation a control would have improved

(1)

accuracy A precision B C repeatability validity D


78

(iii) The table gives some properties of rice seeds and fenugreek seeds. Property of seeds

Rice

Fenugreek

Number per g

200

500

Calcium ion content / mg 100g–1

21

176

Magnesium ion content / mg 100g–1

177

191

The calcium content of one fenugreek seed was calculated to be 3.52 μg. Calculate the calcium content of one rice seed.

(3)

Answer ............................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . μg


79

(iv) After two weeks, the seedlings of both rice and fenugreek grown in both solutions had green leaves. The rice seedlings grown in mineral ion solution without calcium ions were shorter than the rice seedlings grown in mineral solution without magnesium ions. The fenugreek seedlings grown in mineral ions solution without calcium ions grew to normal height. Explain what is shown by these observations.

(3)

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80

(b) The only source of light provided for the plants was from outside the window. All of the seedlings grew towards the window. Explain the reason for this response of these seedlings to light.

(3)

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81

10 Opioids are used to treat moderate to severe pain. They are a group of drugs synthesised from morphine.

(a) Opioids and morphine both affect the size of the pupil of the eye. The graph shows the effects of these drugs on the diameter of the pupil following exposure to a flash of light. Diameter of the pupil / mm

10 Opioid

8

Morphine

6 4 2 0 1 flash of light

2

3

4

5

Time / hours

Calculate the rate of change in pupil diameter between one and five hours after exposure to light for those individuals who had taken morphine.

(2)

Answer ........................................ . . . . . . . . . . . . . . . . mm h–1


82

DO NOT WRITE IN THIS AREA


(ii) Explain the effect of opioids on the diameter of the pupil, between one and five hours after exposure to a flash of light.

(3)

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(iii) Comment on reasons why the results of this investigation may not prove that any changes in pupil size were the direct result of either the opioid or morphine. (4)

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83

BLANK PAGE


84







BLANK PAGE


85

BLANK PAGE


86

Acceptable Answer

as G does not stretch, the contraction of E moves the bone



(1) (1) (1)

carboxyl group / COOH

amine group / NH2

R group





(1)

(1)



A description that makes reference to

Acceptable Answer

C (amino acids joined by peptide bonds)

Answer

G (tendon) attaches E to the bone




Acceptable Answer

contraction (of F ) {flexes / bends } the arm

antagonistic (muscles)

Acceptable Answer








Mark

(1)

Mark

(2)

Mark

(1)

Mark

(1)

Mark


Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

87

Acceptable Answer

Acceptable Answer

Acceptable Answer

opsin released causing sodium ion channels to be blocked

which causes hyperpolarisation in the rod cell

causing action potential in bipolar cell (results in action potential in the optic nerve)








(cis) retinal

rhodopsin

C (phospholipid)

Answer






(1)

(1)

(1)

Mark

(1)

Mark

(1)

Mark

(1)

Mark


Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

88

Acceptable Answer

high blood pressure associated with increased risk of CVD

G has the lowest ratio of HDL to total cholesterol

G has higher ratio of LDL associated with increased risk of CVD







A (P)

Answer

x axis: time AND y axis: voltage / potential difference

Acceptable Answer

higher systolic pressures therefore higher blood pressure



An explanation that makes reference to:

B (F and G)

Answer






(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

(1)

Mark

(1)

Mark

(4)

Mark

(1)

Mark

89

Acceptable Answer

irregular heart rate



(1) (1) (1) (1)

 being { overweight / obese } is a risk factor in developing heart disease

 { fatigue / sleepiness } may stop people exercising

 lack of exercise can lead to further weight gain

(1)

(1)

 side effects of the drug include { weight gain / fatigue / sleepiness }


Acceptable Answer

length of time between T and P is variable



An explanation that makes reference to:

B (Q to R)

Answer


Question Number 3(d)



Mark

(2)

Mark

(1)

Mark


Additional Guidance

Additional Guidance

Additional Guidance

90

B (C - O - C)

B (hydrolysis)

Answer

Answer

(1) 900 mg dm-3

 Correct answer calculated

Additional Guidance

Additional Guidance

Allow full marks for correct answer with no working.

(1) 5 x { 18 /

 Correct conversion to mg

72 ÷ 4 } = 90

(1) 7.5 and 2.5

Additional Guidance

Additional Guidance

 Correct selection of values from graph

Acceptable Answer

 maintenance of internal body conditions within an appropriate range


Acceptable Answer





Question Number 4 (a)

(1)

Mark

(1)

Mark

(3)

Mark

(1)

Mark

91

less glucose for respiration

less { energy / ATP } in muscle tissue





range of enzyme concentration

control of other named variables

measurement of rate of glucose production








Acceptable Answer

low blood glucose levels




Acceptable Answer


Question Number 4(d)(ii)

Question Number 4(d)(i)

Mark

(3)

Mark


Additional Guidance

(1) e.g. temperature, pH, concentration of substrate (1)

(1)

(1)

(1)

(1)

Additional Guidance

92

Acceptable Answer

a (random) change in the sequence of bases in the DNA

involving { deletion / substitution / addition } of a base

this affects the triplet code / changes sequence of amino acids in the enzyme molecule

change in shape of active site










Acceptable Answer

Difference  prokaryotes { do not have a double membrane / possess a cell wall }

(1)

(1)

(1)

(1)

(1)

(1)



both contain { circular DNA / plasmids }

(1)

Similarities  both contain ribosomes


B (matrix)

Answer




Question Number 5 (a)

Additional Guidance

Additional Guidance

Additional Guidance

(3)

Mark

(3)

Mark

(1)

Mark

93

the severity of symptoms is related to the proportion of mitochondria with damaged DNA in the mother only

because (the child’s mitochondria) are derived from the { oocyte / egg cell }

mitochondria in sperm do not enter the egg on fertilisation








Acceptable Answer



(1)

(1)

(1)

(3)

Mark


Additional Guidance

94

so that the volume of oxygen used can be measured



cross-sectional area of tube correctly calculated

volume of oil displaced correctly calculated

correct answer







Acceptable Answer

to absorb carbon dioxide




Acceptable Answer



Question Number 6(a) (i)

Additional Guidance

Allow full marks for correct answer, no working

(1) = 0.26 mm3min-1

(1) 0.385 x 8.2 or 3.157

Example of Calculation (1) 3.14 x 0.35 x 0.35 or 0.385

(1)

(1)

Additional Guidance

(3)

Mark

(2)

Mark

95

Indicative content

5-6

Level 2

Level 3

The description shows a well-developed and sustained line of scientific reasoning which is clear, coherent and logically structured. Total for Question 6 = 11 marks

The description shows some linkages and lines of scientific reasoning with some structure A description of the method to investigate a range of temperatures supported throughout with evidence to produce valid data.

The description will contain basic information with some attempt made to link knowledge and understanding to the given context. A description of the method to investigate a range of temperatures but with some attempt to produce valid data.

Descriptor No awardable content A description of the method to investigate a range of temperatures but with limited attempt to produce valid data. Generalised comments made.

method for setting a constant temperature measurement of a range of temperatures use of the syringe to reset the apparatus using the same mass of seeds repeating measurements at each temperature modifying the left hand tube to have the same volume of air adding potassium hydroxide or killed seeds to the left hand side


3-4

Level 1

      



Mark 0 1-2

Level

Question Number *6(b)

96

Acceptable Answer

Acceptable Answer

transcription of DNA to mRNA

{ translation of mRNA / protein synthesis } on ribosomes






plasmid / virus

ligase / integrase

genome is a complete set of { DNA / introns and exons }



Acceptable Answer

gene is a length of DNA that codes for a { polypeptide / protein }




Acceptable Answer






(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

(2)

Mark

(1)

Mark

(1)

Mark

(2)

Mark

97

no prothrombin activated so thrombin not produced

thrombin needed to convert fibrinogen to fibrin

fibrin needed to trap { platelets / blood cells } to form the (blood) clot








Acceptable Answer



(1)

(1)

(1)

Mark


Additional Guidance

98

Indicative content

5-6

Level 2

Level 3

The explanation shows a well-developed and sustained line of scientific reasoning which is clear and logically structured.

The explanation shows some linkages and lines of scientific reasoning with some structure. An explanation is made which is supported throughout by sustained application of relevant evidence of analysis, interpretation and/or evaluation of both pieces of scientific information.

The explanation will contain basic information with some attempt made to link knowledge and understanding to the given context. An explanation will be given with occasional evidence of analysis, interpretation and/or evaluation of both variables.

Descriptor No awardable content An explanation may be attempted but with limited interpretation or analysis of the scientific information with a focus on mainly just one variable.

if acetylcholine receptors on post synaptic membrane affected, no depolarisation of post synaptic neurone if calcium ion channels affected, vesicles in presynaptic neurone do not fuse with presynaptic membrane no neurotransmitter released if sodium ion channels affected, no depolarisation of axon if potassium ion channels affected, no repolarisation of axon no propagation of action potential


3-4

Level 1

     



Mark 0 1-2

Level

Question Number *8(a)

99

the benefits to humans must outweigh harm done to other animals



to determine safe dose

to determine side effects

to determine how the drug is metabolised







An explanation that makes reference to two of the following:

Acceptable Answer

utilitarian argument, better to test on animals than on humans




Acceptable Answer




(1)

(1)

(1)

(1)

(1)

Mark

(2)

Mark


Additional Guidance

Additional Guidance

100

Mass of one seed correctly calculated

Calcium ion content for one seed calculated

Correct answer





Acceptable Answer



D (validity)

Answer

A (complete mineral ion solution)

Answer






(1) = 1.05 (µg)

(1) (21 × 0.005) ÷ 100 or 0.00105

Example of Calculation: (1) 1 ÷ 200 = 0.005(g)

Additional Guidance

Additional Guidance

Additional Guidance

(3)

Mark

(1)

Mark

(1)

Mark

101

seedlings of rice deficient in calcium ions were shorter due to less calcium ions stored in the seed

seedlings of fenugreek did not suffer calcium ion deficiency due to the greater content of calcium ions in the seed





positive phototropism

IAA diffuses away from light source

IAA accumulates in { cells / tissues } furthest from light

IAA stimulates cell elongation causing growth towards light










Acceptable Answer

seedlings not deficient in magnesium ions, chlorophyll production not affected




Acceptable Answer




(1) (1) (1) (1) (1) (1)

(1)

(1)

(1)

Mark

(3)

Mark


Additional Guidance

Additional Guidance

102

rate of change calculated



Additional Guidance

(1) (1) (1)

 the contraction of the circular muscles of iris stimulated / the contraction of the radial muscles inhibited

 so parasympathetic nerve pathway inhibited / sympathetic nerve pathway stimulated

Additional Guidance

Allow full marks for correct answer, no working

(1) 1.2 ÷ 4 = 0.3

Example of calculation: (1) 5.6 – 4.4 = 1.2 mm

 the pupil constricts with opioids


Acceptable Answer

calculation of change in pupil size



Acceptable Answer




(3)

Mark

(2)

Mark

103

(1) (1) (1)

(1)

 no control with neither morphine or opioids to allow comparison

 light conditions need to be controlled

 no details of how subjects selected to reduce variability in response, e.g. same gender, same age, no other medication

 no indication of sample size or statistical analysis to determine significance of results


Acceptable Answer


Question Number 10(a)(iii) Mark


Additional Guidance

104



Other names

Centre Number

Candidate Number

Biology A (Salters-Nuffield)

Advanced Paper 3: General and Practical Applications in Biology Specimen Paper for first teaching September 2015

Time: 2 hours 30 minutes

Paper Reference

9BN0/03

You may need a ruler, pencil and a calculator.

Total Marks

Instructions

black ink or ball-point pen. • Use Fill in the boxes at the top of this page with your name, • centre number and candidate number. Answer • Show yourall questions. in any calculation questions and include units in your • answer whereworking appropriate. the questions in the spaces provided • A– nswer there may be more space than you need. may use a scientific calculator. • You marked with an asterisk (*), marks will be awarded for your ability • toIn questions structure your answer logically showing how the points that you make are related or follow on from each other where appropriate.

Information

total mark for this paper is 100. • The for each question are shown in brackets • T–heusemarks this as a guide as to how much time to spend on each question.

Advice

each question carefully before you start to answer it. • Read to answer every question. • Try • Check your answers if you have time at the end.

Turn over


3/2/3/


105

Answer ALL questions. Write your answers in the spaces provided. 1 Lead is a toxic metal that can affect the structure of proteins. Lead affects protein in a similar way to changing pH.

Beetroot vacuoles contain a pigment. The absorbance of a solution is proportional to the concentration of the pigment in the solution.

The graph shows the results of a scientific investigation to study the effect of increasing lead concentration on the permeability of the membranes of beetroot cells. 0.27

Absorbance / AU

0.25 0.23 0.21 0.19 0.17 0.15 0

5 10 15 concentration of lead / ‌parts per billion

20

(a) State the name of the membrane that surrounds the vacuole in beetroot cells.

(1)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) Calculate the difference in percentage increase in absorbance between the lead concentration of 0–10 parts per billion and 10–20 parts per billion.

(3)

Answer ........................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . %


106

(c) (i) Explain the effect of lead on membrane permeability in beetroot cells.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Devise an investigation to determine whether pH has a similar effect to lead on the permeability of the membranes of beetroot cells.

(4)

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................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



107

2 A dead human body can supply a variety of evidence to support the time of death.

The table shows the relationship between the mean rectal temperature, calculated from a number of human bodies, and time after death. All bodies were at the same ambient temperature. Time after death / hours

Mean rectal temperature / °C

Range of rectal temperature / °C

4

36

± 1.8

8

31

± 2.5

12

28

±3.3

16

26

±4.3

20

24

±5.1

24

22

±5.6

(a) Deduce the maximum ambient temperature.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) Analyse the data to explain why a more reliable estimate of time of death could be given if the dead body has a higher rectal temperature.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


108

(c) State two features of these bodies that could account for the variation in the data.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(d) Explain why recording rectal temperature is more reliable than measuring skin temperature.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(e) In addition to body temperature, forensic scientists would look for other evidence of time of death.

Give two other pieces of evidence from a body that allow for an estimation of the time of death.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



109

3 DCMU is a herbicide that can disrupt one of the carrier proteins in the electron transport chain of chloroplasts.

A student carried out an investigation to study the effect of DCMU concentration on the Hill reaction.

The student ground up some spinach leaves in an isolation mixture containing sucrose solution at a concentration of 0.4 mol dm–3. The mixture was filtered and then spun in a centrifuge. The chloroplasts were extracted.

These chloroplasts were divided equally into eight different tubes containing a solution of distilled water, DCPIP and a buffer.

A small volume of DCMU was added to each tube and the time taken for the blue DCPIP to decolourise was recorded.

(a) (i) Explain why the isolation mixture contained sucrose at a concentration of 0.4 mol dm–3 rather than at a concentration of 0.8 mol dm–3.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) The isolation mixture had a temperature of 4 °C and pH of 7.

Explain why this temperature and pH are appropriate.

(3)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


110

(b) The time taken for the DCPIP to decolourise was converted to a rate of colour change. The results are shown in the table.

Concentration of DCMU / µmol dm–3

Rate of colour change / × 10–4 s–1

0

23.5

1

12.5

2

6.3

3

4.2

4

3.2

5

2.6

6

2.2

7

2.3

(i) Analyse the data to deduce a null hypothesis for this investigation.

(1)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


111

(ii) The student started to analyse the data using a statistical test, called the Spearman’s rank correlation coefficient (rs ), to see if there was a correlation.

Complete the table by filling in the empty boxes.

(1)

Concentration of DCMU / mol dm–3

Concentration ranked (R1)

Rate of colour change / 10–4 s–1

Rate ranked (R2)

0

1

23.5

8

1

2

12.5

2

3

3

Difference in ranks d (R1–R2)

Difference squared d2

7

5

25

6.3

6

3

9

4

4.2

5

1

1

4

5

3.2

4

1

1

5

6

2.6

3

3

9

6

7

2.2

1

6

36

7

8

2.3

2

6

36

(iii) Calculate rs by using the equation. rs = 1–

6Σ d 2 n(n2 − 1)

Where Σ(d 2) is the sum of all the values for d 2 and n is the number of pairs of data.

rs =


(3)

................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

112

(iv) The table shows some of the critical values for the Spearman’s rank correlation coefficient.

p value

Number of pairs of data (n)

0.10

0.05

0.02

0.01

6

0.829

0.866

0.943

1.000

8

0.643

0.786

0.833

0.881

10

0.564

0.648

0.746

0.794

12

0.506

0.591

0.712

0.777

14

0.456

0.544

0.645

0.715

16

0.425

0.506

0.601

0.665

18

0.399

0.475

0.564

0.625

Explain the outcome of the statistical test.

(3)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



113

4 Sand dunes are a habitat that can often be found by the edge of the sea.

(a) An investigation was carried out to study the variety of plant species found on sand dunes.

Four adjacent sand dunes from the sea to further inland were selected, as shown in the diagram. beach dune 1

sea

dune 2

dune 3

dune 4

Each species of plant present on dune 1 was recorded along with the total number of each species of plant present. This was repeated for dunes 2, 3 and 4 and the results are shown in the table. Plant species

Number of each plant species present dune 1

dune 2

dune 3

dune 4

A

169

9

0

0

B

5

123

19

0

C

0

0

126

182

D

1

44

0

0

E

0

0

5

2

F

0

0

20

10

G

0

0

86

35

H

0

0

0

62

I

0

0

32

17

J

0

0

0

119


114

(i) The diversity index was calculated for dunes 1, 2 and 3 using this equation. Diversity index (D) =

N(N − 1) Σn(n − 1)

Where N is the total number of all individuals of all species in each dune. Use the table and diversity index equation to calculate the diversity index for dune 4.

Plot your answer on the bar chart.

(3)

5.0 4.5 4.0 Diversity index

3.5 3.0 2.5 2.0 1.5 1.0 0.5 0

dune 1

dune 2

dune 3

dune 4


115

(ii) Explain how the data demonstrate the process of succession.

(5)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) Devise a procedure that you could use to find out if the percentage cover of species B is different on the tops of dunes than in between the dunes.

(5)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



116

5 The phenotype of an organism can be influenced by a variety of factors.

Phenotypic plasticity is the mechanism that many organisms use to phenotypically alter due to a change in environmental conditions.

An investigation to study phenotypic plasticity was carried out using a species of freshwater snail.

Newly hatched freshwater snails were used. These snails were divided into three groups and each group was placed in a tank with a different set of conditions.

Three different conditions were used. One was a control and the other two are described in the table.

Condition

Description

A

In water taken from a tank containing predator fish that had eaten some of the snails

B

In water in a tank exposed to ultraviolet light (UV)

(a) Describe a suitable control to be used with the third group of snails.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........................................................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


117

(b) The snails were allowed to grow for eight weeks and then the mean percentage of pigment in the snail shells was assessed for each group. The results are shown in the graph. Mean percentage of pigment in snail shell (%)

80 70 60 50 40 30 20 10 0

control

A

B

(i) Scientists predicted that the snails exposed to both UV light and water from a tank of predator fish would have 80% shell pigmentation.

Explain how this prediction was made.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) It is thought that an increase in shell pigmentation levels provides protection against UV light. UV is a form of radiation that can damage DNA.

Explain how the DNA of the snail could be damaged.

(2)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


118

(c) The phenotype is influenced by the activation of genes.

(i) Describe how a gene can be activated.

(4)

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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(ii) Epigenetic changes can modify the activation of certain genes.

State two types of epigenetic changes that can occur.

(2)

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119

6 There are a number of reactions that regularly occur in cells.

(a) Condensation reactions can be used to join a number of molecules together.

(i) The diagram shows two substrate molecules.

Draw the products when a condensation reaction occurs between the two substrate molecules. CH2OH H HO

H OH H

O H H

OH

CH2OH H HO

OH

(ii) Name the larger product formed in this reaction.

H OH H

(2)

O H H

OH

OH

(1)

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120

*(b) Another reaction that regularly occurs in cells is phosphorylation.

Phosphorylation plays a significant role in a wide range of cellular processes. Over a quarter of a million scientific articles have been written on this subject.

Using your knowledge of biology, discuss the roles of phosphorylation in cells.

(9)

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121

7 The scientific article you have studied is adapted from articles from Nature, Scientific American and the ScienceDaily website.

Use the information from the scientific article and your own knowledge to answer the following questions.

(a) Give the name of the ‘simpler molecules’ produced by the breakdown of glucose that can enter the mitochondria (paragraph 3).

(1)

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(b) (i) Describe the role of oxygen in the ‘last reaction’ involved in aerobic respiration in the mitochondria (paragraph 3).

(1)

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(ii) Explain how carbon monoxide reduces the production of ATP in the electron transport chain (paragraphs 3 and 4).

(3)

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122

(c) Explain how nitric oxide (NO) released by nerve endings could result in vasoconstriction of blood vessels (paragraphs 7 and 9).

(3)

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123

(d) Explain how free radicals may be involved in the production of P53 in the cell (paragraph 17).

(3)

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(e) Describe three structural differences between the inner mitochondrial membrane and the outer mitochondrial membrane (paragraphs 18 and 19).

(3)

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124

(f ) Long wavelengths of light, in the near infrared (NIR) spectrum, appear to be able to modulate cell respiration by affecting cytochrome oxidase (paragraph 30).

Deduce how this may explain why NIR phototherapy has ‘shown promise’ in reducing cell death caused by myocardial infarction (paragraph 34).

(4)

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125

(g) (i) Describe how scientists could have produced ‘genetically modified neurons’ described in paragraphs 38 and 39.

(4)

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(ii) A light sensitive protein is channelrhodopsin-2. This is a channel protein that spans membranes. When exposed to blue light these channel proteins open and allow sodium ions to flow through.

Explain how a brief flash of light could cause neurotransmitter to be released by ‘the genetically modified neurons’ (paragraphs 38 and 39).

(5)

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126

(h) Explain how fMRI allowed Vandewalle to make the observations described in paragraph 50.

(3)

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Every effort has been made to contact copyright holders to obtain their permission for the use of copyright material. Pearson Education Ltd. will, if notified, be happy to rectify any errors or omissions and include any such rectifications in future editions.


127

BLANK PAGE


128


Biology A (Salters-Nuffield)

Advanced Paper 3 - Pre-release material Specimen Paper for first teaching September 2015

Paper Reference

9BN0/03

Do not return the insert with the question paper.

Turn over


3/2/3/

*S49423A*


129

Power Games 1 Seventy-five years ago, Otto Warburg’s star was at its zenith. The pioneering German biochemist delivered his Nobel address in December 1931. He described the ingenious experiments by which he had unmasked the enzyme responsible for the critical step of cell respiration, the process that turns the energy in chemical compounds into energy the cell can use. His work on respiration in the early 1930s nearly earned him a second Nobel, ultimately denied him by Hitler. Then his star began sinking. His ideas on the importance of cell respiration in cancer led many to dismiss him as a crank. And the rise of molecular genetics in the 1960s put such ideas into a far distant orbit. 2 But now, Warburg’s star is rising again. A new generation of researchers is returning to his ideas about respiration in cancer cells. Recent findings suggest that the enzyme he identified, cytochrome oxidase, is a key player in a new understanding of how the cell’s energy metabolism affects health and disease. And surprisingly they show that light has a profound effect on how the enzyme works – and could even be used to treat degenerative disease. 3 To extract energy from molecules, the cell first breaks down glucose into simpler molecules via a process called glycolysis. It then feeds these molecules into energy-producing structures called mitochondria, which strip electrons from them to produce energy with the help of oxygen. As Warburg showed, cytochrome oxidase governs the last reaction in this process. 4 Perhaps the most surprising aspect of the renaissance of Warburg’s ideas is that the methods he used to make this discovery matter again. They exploit two chemical quirks: carbon monoxide (CO) can block respiration by binding to cytochrome oxidase in place of oxygen; and a flash of light can displace it, freeing up the site for oxygen to bind again. Self control 5 By measuring oxygen consumption at different wavelengths of light, Warburg worked out that the enzyme belonged to a group of proteins that include haemoglobin and chlorophyll. But for Warburg, the binding of CO to the enzyme was just an oddity he could put to good use. He had no inkling that biology might use the same trick. 6 Yet over the past decade, researchers have come to appreciate that cells often use CO, and to an even greater extent NO (nitric oxide), to block respiration. Not only that, but light has striking counter-effects on cytochrome oxidase. And all these suitors to the enzyme turn out to be critical to our understanding not just of cancer, but practically all degenerative diseases. 7 Nitric oxide is emitted by nerve endings and can act on an enzyme called guanylate cyclase to relax blood vessels – the impotence drug Viagra manipulates this system. For a long time, scientists thought that guanylate cyclase was NO’s only target. But in the mid-1990s, they found that the molecule can also bind to cytochrome oxidase and hinder respiration. What’s more, it could do so at levels found in the body’s tissues. 8 The finding that the body could poison one of its own enzymes was initially shrugged off as an imperfection – an example of how evolution cobbles organisms together with no forethought. But a few years later, several groups reported that mitochondria harboured an enzyme that synthesizes NO. Why would cells go out of their way to cook up NO right next to the respiratory enzymes?

2 Pearson Edexcel Level 3 Advanced Level GCE in Biology A (Salters-Nuffield) Specimen Papers - Issue 1 - October 2015 © Pearson Education Limited 2015

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9 According to cell biologist Salvador Moncada of University College London, evolution really has crafted cytochrome oxidase to bind not only oxygen but also NO. “One effect of slowing respiration in some locations is to divert oxygen elsewhere in cells and tissues,” he says. This prevents oxygen levels sinking dangerously low. Moncada, for example, has shown that NO blocks respiration in the cells lining blood vessels and that this helps to transfer oxygen into smooth muscle cells in these vessels. Fireflies use a similar trick to flash light. Flashing the gauntlet 10 Firefly flashes have lit up the human imagination since antiquity. Light is produced by the action of the luciferase enzyme, which uses ATP to activate luciferin to a luciferyl adenylate intermediate. This in turn reacts spontaneously with oxygen to emit a photon, giving rise to bioluminescence. 11 The sequence of flashes, which often beam complex messages to potential mates, clearly requires exquisite nervous control. But no nerve cells connect directly to the ‘lantern’ cells that produce the light, suggesting that some kind of intermediary is needed to ferry messages from the nerve endings. 12 Barry Trimmer and his colleagues at Tufts University in Medford, Massachusetts, have shown that this is likely to be NO and suggest it works by binding to cytochrome oxidase. To do so, it exploits a neat feature of the firefly’s breathing system. 13 Insects breathe through tubules, called trachea, that connect the outside world to cells in the body via a network of increasingly fine branches. The ends of these, called tracheoles, abut cells and allow oxygen to diffuse outwards. In fireflies, when oxygen passes from tracheoles into the lantern cells, it must run the ‘gauntlet’ – a dense ring of energy-producing structures called mitochondria in the periphery of the lantern cells. 14 Normally, the oxygen would bind to cytochrome oxidase in the mitochondria and be used in respiration. But when NO is released from the nerve endings, it binds to cytochrome oxidase, blocking respiration and diverting oxygen through the gauntlet into the lantern cell. 15 There, oxygen reacts with the luciferyl intermediate to produce a flash of light. The glory is that the flash switches itself off. Light dissociates NO from cytochrome oxidase, allowing oxygen to bind again. Now the mitochondria consume oxygen once more, allowing the luciferyl intermediate to build up until another wave of NO arrives. 16 But the consequences of blocking respiration go beyond diverting oxygen. Respiration, Moncada argues, is not just about generating energy, it’s about generating feedback that allows a cell to monitor and respond to its environment. Blocking respiration generates chemical signals, in the form of highly reactive molecules called free radicals. These are normally associated with cell damage, but now it seems they can interact with the proteins that control gene activity and adapt cells to changing circumstances. “Free radicals had a bad reputation,” says pathologist Victor Darley-Usmar, of the University of Alabama, Birmingham. “But we now see them as signals.” 17 In the past few years, researchers have compiled a list of these proteins, or transcription factors, the activity of which depends, at least in part, on interactions with free radicals. These include many proteins known to be linked to cellular life and death, such as P53, a protein that kills cells if they show signs of turning cancerous. “The question is,” says Darley-Usmar, “how is the whole system controlled?”

S49423A Pearson Edexcel Level 3 Advanced Level GCE in Biology A (Salters-Nuffield) Specimen Papers - Issue 1 - October 2015 © Pearson Education Limited 2015

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18 The answer lies in the tens of thousands of protein machines that line each mitochondrion. Organized into chains, they pass electrons extracted from broken-down glucose on to each other. The end-point of the chain is cytochrome oxidase, which catalyses the final step of respiration, in which electrons and protons are transferred onto oxygen to form water. Energy released by this process is used to pump protons over a membrane, creating an electrical charge. The cell can then use this charge to power an enzyme that makes ATP, a molecule that fuels chemical reactions in the cell. 19 The cell can suppress the number of free radicals coming from these respiratory chains by allowing protons to leak back though the membrane without driving the synthesis of ATP, a process known as uncoupling. Undercover radicals 20 But if uncoupling doesn’t bring free-radical leak under control, the signal may be amplified. “There’s a cross-talk, known as the retrograde response, between the mitochondria and genes in the nucleus, which we’re only just beginning to explore,” says cell biologist Keshav Singh of the Roswell Park Cancer Institute in Buffalo, New York, who helped uncover this mechanism. “If we can modulate this signalling, we might be able to influence the life or death of cells in many pathologies, even ageing.” 21 In cancer cells, something goes awry with this pathway. Free radicals can trigger two steps in carcinogenesis, chromosomal instability and metastasis, by hindering DNA repair and promoting the activity of genes involved in cancer spread. “We’ve found that damaged mitochondria, which overproduce free radicals, under-mine the integrity of the nuclear genome in otherwise normal cells,” says Singh. 22 Ultimately, however, the most intractable problem with cancer cells is their failure to undergo apoptosis (cell suicide). There are echoes of Warburg here, for he argued that cancer cells revert to a primitive type that has little or no need for oxygen or mitochondria, depending instead on anaerobic forms of 23, energy generation such as glycolysis. Whether cells really ‘revert’ is a moot point, but Moncada has shown that cells’ ability to switch to glycolysis is critical to their survival. 23 Moncada’s findings suggest that cells that can do without mitochondria – many stem cells, for example, which have been implicated in cancer – can have their resistance to apoptosis stiffened by NO binding to cytochrome oxidase, making cancer more likely. At the same time, cells that depend on mitochondria for energy, such as neurones, may be pushed to apoptosis by NO binding, making degenerative disease more likely. 24 Any solution to excessive NO binding might lower the risk of both cancer and degenerative diseases, as it would make apoptosis more likely in cancer cells and less likely in normal cells. And the second essential feature of Warburg’s experiments – light – might do just that. 25 Light has long been known to promote wound healing, but the detailed molecular mechanisms have only recently been studied. Light’s effects are more than skin deep: at long wavelengths, in the near infrared (NIR) spectrum, photons may penetrate several centimetres into the body. 26 And according to photobiologist Tiina Karu, at the Russian Academy of Sciences in Moscow, NIR rays in exactly this range modulate cell respiration and the signals it generates.


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Light works 27 Karu’s group has explored a number of changes taking place in cultured cells in response to NIR rays. The immediate effect is an energy ‘buzz’, in which ATP levels are stoked up and the electrical charge across the mitochondrial membrane is strengthened. A few hours later, the activity of as many as 110 genes shifts in concert. These genes orchestrate a prolonged rise in mitochondrial energy production, as well as stress resistance. They also prompt cells to cling more strongly to their surroundings, an important factor in wound healing. 28 Exactly how NIR light interacts with the enzyme to bring about these changes is unclear, and difficult to measure. One idea is that phototherapy might work by dissociating NO from the enzyme, so reversing the signalling consequences of excessive NO binding. 29 “We have shown that light can indeed reverse the inhibition caused by NO binding to cytochrome oxidase, both in isolated mitochondria and in whole cells,” says biochemist Guy Brown, at the University of Cambridge, UK. “And what’s more, we found that light can protect cells against NO-induced cell death.” 30 He has a reservation, however. These experiments used light in the visible spectrum, with wavelengths from 600 to 630 nm. Although Brown acknowledges that cytochrome oxidase absorbs NIR photons from 700 to 900 nm, he points out that the absorption takes place in part of the enzyme not involved in NO binding. NIR also seems to have effects on cytochrome oxidase in conditions where NO is unlikely to be present. Presumably then, says Brown, NIR must also have a direct effect on the enzyme. 31 Regardless of the exact mechanism, the effect is to relieve a blockade of the enzyme, whether by NO or any other molecules. According to toxicologist Janis Eells, at the University of Wisconsin, Milwaukee, such relief lowers the likelihood of apoptosis in many conditions. 32 Eells and her colleagues found that NIR phototherapy counters methanol poisoning, which injures the retina and optic nerve, often causing blindness. The toxic metabolite is formic acid, which inhibits cytochrome oxidase. “In a rat model, NIR phototherapy is able to restore virtually normal retinal function, at least as judged by the electroretinogram,” says Eells. 33 And neurobiologist Margaret Wong-Riley and her colleagues at the Medical College of Wisconsin in Milwaukee have shown that NIR phototherapy can also oppose the effects of cyanide on cell cultures. Cyanide poisons by binding to cytochrome oxidase. Wong-Riley’s team showed that phototherapy could halve the rate of apoptosis in cultured neurones, even when given before cyanide treatment. 34 But can NIR phototherapy relieve not just acute toxicity, but more chronic inflammatory conditions? The signs augur well. Eells and her colleagues have shown that NIR phototherapy could cut the rate of apoptosis by 50% in a rat model of retinitis pigmentosa, in which photoreceptors die by apoptosis during postnatal development causing retinal degeneration and blindness. The use of NIR phototherapy on other conditions in which cells die by apoptosis, including acute ischaemic stroke and myocardial infarction, has also shown promise in animal models, and should soon enter clinical trials. 35 So will it work? “The trouble is that if you enthuse about light as a therapy, clinicians and even researchers tend to back away,” says Eells. “Perhaps if the physical interactions of photons with cytochrome oxidase and NO are better known, people will begin to appreciate the huge potential benefits of this technique.” S49423A Pearson Edexcel Level 3 Advanced Level GCE in Biology A (Salters-Nuffield) Specimen Papers - Issue 1 - October 2015 © Pearson Education Limited 2015

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How to Use Light to Control the Brain 36 In the film Amèlie, the main character is a young eccentric woman who attempts to change the lives of those around her for the better. One day Amèlie finds an old rusty tin box of childhood mementos in her apartment, hidden by a boy decades earlier. After tracking down Bretodeau, the owner, she lures him to a phone booth where he discovers the box. Upon opening the box and seeing a few marbles, a sudden flash of vivid images come flooding into his mind. Next thing you know, Bretodeau is transported to a time when he was in the schoolyard scrambling to stuff his pockets with hundreds of marbles while a teacher is yelling at him to hurry up. 37 We have all experienced this: a seemingly insignificant trigger, a scent, a song, or an old photograph transports us to another time and place. Now a group of neuroscientists have investigated the fascinating question: Can a few neurons trigger a full memory? 38 In a new study, published in Nature, a group of researchers from MIT showed for the first time that it is possible to activate a memory on demand, by stimulating only a few neurons with light, using a technique known as optogenetics. Optogenetics is a powerful technology that enables researchers to control genetically modified neurons with a brief pulse of light. 39 To artificially turn on a memory, researchers first set out to identify the neurons that are activated when a mouse is making a new memory. To accomplish this, they focused on a part of the brain called the hippocampus, known for its role in learning and memory, especially for discriminating places. Then they inserted a gene that codes for a light-sensitive protein into hippocampal neurons, enabling them to use light to control the neurons. 40 With the light-sensitive proteins in place, the researchers gave the mouse a new memory. They put the animal in an environment where it received a mild foot shock, eliciting the normal fear behavior in mice: freezing in place. The mouse learned to associate a particular environment with the shock. 41 Next, the researchers attempted to answer the big question: Could they artificially activate the fear memory? They directed light on the hippocampus, activating a portion of the neurons involved in the memory, and the animals showed a clear freezing response. Stimulating the neurons appears to have triggered the entire memory. 42 The researchers performed several key tests to confirm that it was really the original memory recalled. They tested mice with the same light-sensitive protein but without the shock; they tested mice without the light-sensitive protein; and they tested mice in a different environment not associated with fear. None of these tests yielded the freezing response, reinforcing the conclusion that the pulse of light indeed activated the old fear memory. 43 In 2010, optogenetics was named the scientific Method of the Year by the journal Nature Methods. The technology was introduced in 2004 by a research group at Stanford University led by Karl Deisseroth, a collaborator on this research. The critical advantage that optogenetics provides over traditional neuroscience techniques, like electrical stimulation or chemical agents, is speed and precision. Electrical stimulation and chemicals can only be used to alter neural activity in nonspecific ways and without precise timing. Light stimulation enables control over a small subset of neurons on a millisecond time scale.


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44 Over the last several years, optogenetics has provided powerful insights into the neural underpinnings of brain disorders like depression, Parkinson’s disease, anxiety, and schizophrenia. Now, in the context of memory research, this study shows that it is possible to artificially stimulate a few neurons to activate an old memory, controlling an animals’ behavior without any sensory input. This is significant because it provides a new approach to understand how complex memories are formed in the first place. 45 Lest ye worry about implanted memories and mind control, this technology is still a long way from reaching any human brains. Nevertheless, the first small steps towards the clinical application of optogenetics have already begun. A group at Brown University, for example, is working on a wireless optical electrode that can deliver light to neurons in the human brain. Who knows, someday, instead of new technology enabling us to erase memories á la Eternal Sunshine of the Spotless Mind, we may actually undergo memory enhancement therapy with a brief session under the lights. Study of totally blind people shows how light helps activate the brain 46 Light enhances brain activity during a cognitive task even in some people who are totally blind, according to a study conducted by researchers at the University of Montreal and Boston’s Brigham and Women’s Hospital. The findings contribute to scientists’ understanding of everyone’s brains, as they also revealed how quickly light impacts on cognition. “We were stunned to discover that the brain still respond significantly to light in these rare three completely blind patients despite having absolutely no conscious vision at all,” said senior co-author Steven Lockley. 47 “Light doesn’t just allow us to see, it tells the brain whether it’s night or day which in-turn ensures that our physiology, metabolism and behavior are synchronized with environmental time.” “For diurnal species like ours, light stimulates day-like brain activity, improving alertness and mood, and enhancing performance on many cognitive tasks,” explained senior co-author Julie Carrier. The results indicate that their brains can still “see,” or detect, light via a novel photoreceptor in the ganglion cell layer of the retina, different from the rods and cones we use to see. 48 Scientists believe, however, that these specialized photoreceptors in the retina also contribute to visual function in the brain even when cells in the retina responsible for normal image formation have lost their ability to receive or process light. A previous study in a single blind patient suggested that this was possible but the research team wanted to confirm this result in different patients. To test this hypothesis, the three participants were asked to say whether a blue light was on or off, even though they could not see the light. “We found that the participants did indeed have a non-conscious awareness of the light – they were able to determine correctly when the light was on greater than chance without being able to see it,” explained first author Gilles Vandewalle. 49 The next steps involved looking closely at what happened to brain activation when light was flashed at their eyes at the same time as their attentiveness to a sound was monitored. “The objective of this second test was to determine whether the light affected the brain patterns associated with attentiveness -- and it did,” said first author Olivier Collignon.

S49423A Pearson Edexcel Level 3 Advanced Level GCE in Biology A (Salters-Nuffield) Specimen Papers - Issue 1 - October 2015 © Pearson Education Limited 2015

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50 Finally, the participants underwent a functional MRI brain scan as they performed a simple sound matching task while lights were flashed in their eyes. “The fMRI further showed that during an auditory working memory task, less than a minute of blue light activated brain regions important to perform the task. These regions are involved in alertness and cognition regulation as well being as key areas of the default mode network,” Vandewalle explained. Researchers believe that the default network is linked to keeping a minimal amount of resources available for monitoring the environment when we are not actively doing something. “If our understanding of the default network is correct, our results raise the intriguing possibility that light is key to maintaining sustained attention” agreed Lockley and Carrier. “This theory may explain why the brain’s performance is improved when light is present during tasks.” Study of totally blind people shows how light helps activate the brain, October 28, 2013 http://www.sciencedaily.com/releases/2013/10/131028090408.htm Power Games NATURE, Vol 443, 26 October 2006 News Feature by Nick Lane How to Use Light to Control the Brain Shades of Proust: Using “optogenetics,” researchers are able to trigger a memory Scientific American March 27, 2012 by Stephen Dougherty

Every effort has been made to contact copyright holders to obtain their permission for the use of copyright material. Pearson Education Ltd. will, if notified, be happy to rectify any errors or omissions and include any such rectifications in future editions. 8 Pearson Edexcel Level 3 Advanced Level GCE in Biology A (Salters-Nuffield) Specimen Papers - Issue 1 - October 2015 © Pearson Education Limited 2015

S49423A 136

interferes with { tertiary / 3-D } shape of the channel proteins

therefore causes channel proteins to open

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


Acceptable Answer

 difference in percentage

(1)

(1)

Additional Guidance


(1) Example of calculation: 35.3% ÷ 13.0% (1) = 22.3%

 calculation of percentage

Additional Guidance (1) 0.17 AU , 0.23 AU , 0.26 AU

Acceptable Answer

Additional Guidance

 selection of correct points from the graph

Tonoplast

Acceptable Answer






(2)

Mark

(3)

Mark

(1)

Mark

137

solutions with a range of pH values

pieces of beetroot of same surface area

control of other named relevant variables

measurement of absorbance of solution using colorimeter

repeats at each pH value to calculate mean

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







An answer that makes reference to four of the following:

Acceptable Answer



(1)

Mark


e.g. temperature / volume of (1) solution / time left in solution /

(1)

(1)

(1)

Additional Guidance

138

after 24 hours, lowest body temperature 22 minus 5.60C

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only the highest temperature shows no overlap

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body size

fat level

position of body i.e. in fetal position or not

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




Acceptable Answer

range smaller at higher temps

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Acceptable Answer

correct reading of temperatures

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Acceptable Answer





(1)

(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

Example of calculation 22 – 5.6 = (lower than / equal to) 16.4OC

(1) Accept calculation of maximum ambient temperature

(1) 22 ±5.6

Additional Guidance

(2)

Mark

(2)

Mark

(2)

Mark

139

skin surface temperature would be more variable

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rigor mortis

degree of decomposition

forensic entomology

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


Acceptable Answer

rectal temperature is core temperature / it would be 37OC at time of death

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Acceptable Answer


Question Number 2(e)


(1)

(1)

(1)

(1)

(1)

Mark

(2)

Mark


Additional Guidance

Additional Guidance

140

no net loss of water from the chloroplast from osmosis



pH 7.0 so enzymes not denatured

so RUBISCO remains active

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

7 and 49

Acceptable Answer

There is no correlation between the concentration of DCMU and the rate of DCPIP colour change

Acceptable Answer

low temperature to (temporarily) slow enzyme activity

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Acceptable Answer

there is no concentration gradient present between the chloroplast and the isolation solution

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Acceptable Answer






(1)

(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

Additional Guidance

Additional Guidance

(1)

Mark

(1)

Mark

(3)

Mark

(2)

Mark

141

Correct calculation of denominator

Correct calculation of correlation coefficient

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

Selection of appropriate critical value from the table

calculated value is greater (than critical value)

Can reject the null hypothesis / correlation is significant

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Acceptable Answer

Correct calculation of numerator



Acceptable Answer


Question Number 3(b)(iv)

Question Number 3(b)(iii) (Σd2 = 996) ÷ (n(n2-1) = 504)

Example of calculation:

(1)

(1)

Mark

(3)

Mark


(1) 0.786 , 0.833 , 0.881

Additional Guidance

Allow all marks for correct answer with no working

(1) = (-) 0.976

(1)

(1)

Additional Guidance

142

correct calculation of denominator

correct calculation of diversity index / correctly plotted on the graph

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

succession is the sequence of { species / communities } replacing each other with time

dune 4 is older than dune 1

no species of plant inhabits all 4 dunes /example from table quoted to show one species inhabiting no more than 3 dunes

plant diversity increases with time

description of increasing diversity index from dune 1 to dune 4

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

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

An explanation that makes reference to the following points:

Acceptable Answer

correct calculation of numerator



Acceptable Answer




(1)

(1)

(1) e.g. species G only found on dunes 3 and 4

(1)

(1)

Additional Guidance


(1) = 3.48 ;

Example of calculation: (1) (N(N-1) = 427 x 426 = 181 902) ÷ (Σn(n-1) =) 52 320) (1)

Additional Guidance

(5)

Mark

(3)

Mark

143

systematic sampling

quadrats used at the tops and in between dunes

details of method used for measuring percentage cover

repeats to make a valid comparision

a named relavent statistical test

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







An answer that makes reference to the following points:

Acceptable Answer



(1)

(1)

(1)

(1)

(1)

Mark


Additional Guidance

144

water added but not from tank with fish in it that have eaten snails

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adding effects of ‘fish’ and ‘UV’

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interferes with DNA replication

(potentially) leading to mutations

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


Acceptable Answer

calculating increase above control for ‘fish’ and for ‘UV’




Acceptable Answer

no UV




Acceptable Answer





Additional Guidance

(1)

(1)

(1)

Additional Guidance

(1) fish exposure effect is 12% (above control) and (UV is) 28%

(1)

(1)

Additional Guidance

(2)

Mark

(2)

Mark

(2)

Mark

145

Binds to promotor region

RNA polymerase binds

mRNA to be synthesised

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



DNA methylation

histone modification






Acceptable Answer

transcription factor




Acceptable Answer




(1)

(1)

(1)

(1)

(1)

(1)

Mark

(4)

Mark


Additional Guidance

Additional Guidance

146

maltose

glycosidic bond drawn correctly



Acceptable Answer

water




Acceptable Answer




(1)

(1)

Additional Guidance

Additional Guidance

(1)

Mark

(2)

Mark

147

Indicative content

4-6

7-9

2

3

148


Scientific argument is well developed and logical. Demonstrating throughout the skills of synthesising and integrating relevant knowledge with consistent linkages to biological concepts and/or ideas, leading to nuanced and balanced scientific argument or decision/conclusion based on evidence.

Scientific reasoning supported throughout by sustained linkage of a range of scientific ideas, processes, techniques and procedures.

Scientific argument is partially developed. Attempts to synthesise and integrate relevant knowledge with linkages to biological concepts and/or ideas, leading to a notional scientific argument or decision/conclusion. Demonstrates comprehensive knowledge and understanding by selecting and applying relevant knowledge of biological facts/concepts to support an argument or decision/conclusion being made.

Scientific reasoning occasionally supported through the linkage of a range of scientific ideas, processes, techniques and procedures.

Scientific arguments may be attempted, but fails to link biological concepts and/or ideas in order to support decision/conclusion. Limited attempt to address the question. Demonstrates adequate biological knowledge and understanding with selection of some biological facts/concepts to support an argument or decision/conclusion being made.

Provides little or no references to a range of scientific idea, processes, techniques and procedures.


1-3

Candidates are expected to offer a range of appropriate examples to support a comment on the roles of phosphorylation in Biology.  Description of phosphorylation as an addition of phosphate.  Examples of phosphorylation in respiration to include glycolysis, oxidative phosphorylation, substrate level phosphorylation.  Examples of phosphorylation in photosynthesis to include RuBP, GP, NADP, non-cyclic photophosphorylation.  Role of phosphorylation of ADP to store energy.  Phosphorylation of lipids to make phospholipids and their roles in membranes.  Addition of phosphates to help form the DNA backbone / involved in phosphodiester bonds.  Appreciation of the consequences of phosphorylation such as activation of molecule for further reactions. Mark Descriptor 0 No rewardable material Demonstrates isolated elements of biological knowledge and understanding.


Answers will be credited according to candidates’ deployment of knowledge and understanding of material in relation to the qualities and skills outlined in the generic mark scheme.

1

Level

6(b)

Question Number

Acceptable Answer

Final electron acceptor

carbon monoxide binds to cytochrome oxidase

prevents oxygen binding to the enzyme

blocks the electron transport chain / prevents oxidation of reduced electron carriers











Acceptable Answer

pyruvate and { reduced coenzyme / reduced NAD }

Acceptable Answer





(1)

(1)

(1)

Additional Guidance

Additional Guidance

Additional Guidance

(3)

Mark

(1)

Mark

(1)

Mark

149

diverts oxygen to smooth muscle cells

contraction of muscle cells causes vasoconstriction in arterioles





free radicals interact with transcription factors

activation of gene for P53

production of mRNA from activated gene

translation of mRNA resulting in synthesis of P53 on ribosomes









An answer that makes reference to three of the following:

Acceptable Answer

NO binds to cytochrome oxidase in endothelium (of blood vessels)




Acceptable Answer




(1)

(1)

(1)

(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

(3)

Mark

(3)

Mark

150

(1) (1)

only inner membrane contains { ETC (proteins) / ATP synthase / stalked particles }

only inner membrane contains H+ pump





myocardial infarction causes cell death in the heart

due to lack of oxygenated blood reaching cardiac muscle cells

NIR affects cytochrome oxidase involved in aerobic respiration

diversion of oxygen to cardiac muscle cells would reduce death of these cells










(1)

(1)

(1)

(1)

(1)

outer membrane is impermeable to H+ ions



Acceptable Answer

(1)

inner membrane { is folded / has a larger surface area / has cristae }



A description that makes reference to three of the following:

Acceptable Answer


Question Number 7(f)

Question Number 7(e)

Additional Guidance

Additional Guidance

(4)

Mark

(3)

Mark

151

extraction of gene that codes for light-sensitive protein

use of a suitable vector

insertion of gene into the { genome / DNA } in the nucleus of the neurone







{ depolarisation / action potential } occurs

(nerve) impulse reaches { synapse / presynaptic membrane }

calcium ion channels open causing calcium ions to enter presynaptic neurone

vesicles containing neurotransmitter fuses with presynaptic membrane

neurotransmitter released












Acceptable Answer

restriction endonuclease enzyme




Acceptable Answer


Question Number 7(g)(ii)

Question Number 7(g)(i)

(1)

(1)

(1)

(1)

(1)

(1)

(1)

(1)

(1)

Additional Guidance

Additional Guidance

(5)

Mark

(4)

Mark

152

fMRI detects changes in blood flow in the brain

MRI signal reflects state of haemoglobin / magnetic fields repelled by oxygen rich blood / deoxygenated haemoglobin more magnetic than oxygenated haemoglobin

allows areas of greater brain activity to be detected as an image created by magnetic resonance

areas of the brain that are involved in an auditory memory task { were using more oxygen / had an increased flow of blood }










Acceptable Answer


Question Number 7(h)

(1)

(1)

(1)

(1)

Mark


Additional Guidance

153

A Level Bio Spec MOCK

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