Bio Model Ans U2 Describe the transport of proteins in the cell 1. protein made at ribosomes when translated by mRNA 2. protein enters RER cavity; and packaged (in rER 3. packaged into membrane-bound vesicles, vesicles form; move to Golgi 3. vesicles fuse with the Golgi body and protein moves through Golgi 4.Golgi body modifies protein; e.g. adds carb. to make a glycoprotein 5. secreted via vesicles (if extracellular e.g. enzyme); fuses w membrane Describe the structure of the sperm cell nucleus (or any human nucleus) 1. Double membrane; with envelope present & nuclear pores present 2. Contains 23 chromosomes/is haploid (if gametes e.g. sperm/egg) 3. Contains 46 chromosomes/is diploid (if somatic cells) Why we test on animals/rats 1. Laboratory animals are of reduced genetic variation 2. Rats have a similar metabolism (to humans) 3. No harm done to humans 4. Look for potential toxicity or side effects 5. Ethical/Legal Issues (e.g. Rats do not give consent therefore not ok) Why Xylem Tissue is Adapted For Its Role 1. Role: to transport water and minerals; while supporting the plant 2. Hollow lumen/tubes: allows vertical movement of water 3. Pores: allows the sideways movement of water 4. Waterproof: keeps water in xylem tissue and prevents water loss 5. Extra Lignin (and 6. Ring Structure) - gives strength and flexibility How Gene Expression Leads To Specialization of Cell 1. Stimulus (e.g. Chemical stimulus) 2. Deactivates/Activates a specific gene 3. mRNA is transcribed from the only active gene; goes to cytoplasm 4. mRNA is translated; leads to protein synthesis 5. changes structure/func. permanently modifies cell; specialization How to show totipotency in plants (Steps for experiment) 1. Use sharp scissors to cut explant from plant/both plants etc. 2. Use aseptic conditions (e.g. use sterile equipment, clean bench before) 3. Ref. to growth regulators (and Agar) 4. Grow explant into callus 5. Cells can differentiate to become whole plants 6. Control temp - incubator, control light - lightbank, pH - buffer solution Structural Difference Between Sperm Cells and Egg Cells 1. Sperm have FLAGELLUM - egg cells do not 2. Sperm have more STREAMLINED shape - egg cells are circular 3. Sperm have more MITOCHONDRIA - egg cells have less 4. Sperm have ACROSOME - egg cells do not 5. Egg cells have ZONA PELLUCIDA - sperm do not 6. Egg cells have CORTICAL GRANULES - sperm do not 7. Egg cells have less CYTOPLASM - sperm has less Why cold & dry conditions are used in Seedbanks 1. Inhibits germination of seeds 2. Slows down enzyme activity 3. Delays the rate of decay or microbial activity 4. Therefore, prolongs the survival of the seed 5. Drying reduces freezing effect of seeds. Why seeds need to be checked at intervals 1. To check/test for seed viability & check decay/death 2. Allows new seeds to be produced 3. Due to decay or death; stored seeds may need to replaced Nitrogen Ions in Plants 1. Greater protein content (as a result of greater nitrogen uptake of plant) 2. Nitrogen is part of amino acids; used in protein synthesis 3. Amino acids are used to synthesise proteins Role of regulatory authorities (stem cells) 1. Decide on maximum age of embryo allowed for stem cell research 2. Ensure all researchers are following a set code of practice 3. Decide on what is acceptable and what is not 4 .Check that the source of the stem cells is acceptable 5. Stop cloning of humans 6. Ensure that research is not repeated if it has already been tested etc. Description of Plant Cell Wall 1. Cellulose arranged as microfibrils - microfibrils are bundles 2. Cellulose molecules are held together by hydrogen bonds 3. In primary cell wall - cellulose microfibrils are criss-crossed; no lignin 4. In secondary cell wall - cellulose in sheets & lignin is present 5. This arrangement gives the plant cell strength & flexibility 6. Microfibrils used to make ropes (due to their properties) Describe the structure of starch 1. Starch is made up of many a (alpha) glucose monomers 2. Starch is storage of energy - stores glucose (respiratory substance) 3. Starch is large; is unreactive, insoluble (no osmotic effect) 4. (Amylose; coiled & compact, more can be stored in same space) 5. (Amylopectin; branched, 1,6 glyc. bonds - can be easily hydrolysed)
Genetic Diversity vs. Species Richness 1. GD considers one species but SR considers different species 2. GD considers alleles and genotype; SD considers species within area How Acrosome Reaction is Triggered 1. Stimulus - sperm makes contact with the zona pellucid 2. The acrosome swells; and fuses w/ sperm cell membrane 3. Digestive enzymes released via exocytosis 4. Enzymes digest zona pellucida; allow sperm cell to penetrate Why organs are more complex than tissues 1. Organs are made up of a group of similar tissues; 2. Which are made up of many different cell types 3. Organs usually have more than 1 function; various functions Discuss Similarities and Differences between Cellulose and Starch 1. Both made up of glucose (starch - alpha glucose, cellulose - beta) 2. Both have 1,4 glycosidic bonds made via condensation reactions 3. Starch is composed of two types of molecule (amylose/amylopectin) 4. Cellulose has a straight chain; starch (amylopectin) has branching (1,6) 5. Monomers have same orientation in starch; every other inverted in cel. Prophase 1. Chromosomes/chromatids condense and become visible 2. Chromosomes seen as pairs/sister chromatids - centromere holds pair 2. Nuclear envelope (double nuclear membrane) breaks down 3. Nucleolus no longer visible 4. Centrioles move in; go to opposite ends/poles of the cell 5. Spindle fibre starts to form Metaphase 1. Chromosomes/chromatids at equator of cell 2. Chromatids are attached to each other at equator 3. Centromere is complete 4. Spindle is formed and is complete Anaphase 1. Chromosomes/chromatids are separated/pulled apart (not at equator) 2. Chromatids are separated/pulled apart 3. Centromere splits 4. Fibres are shorter (spindle is contracting therefore shorter) Telophase 1. Chromosomes will become invisible/decondense 2. Nuclear envelope and nucleolus will form/reappear/become visible 3. Spindle is no longer visible; has contracted/break down 4. Two separate nuclei now visible; each cell will have centrioles 5. Cytoplasm forms around nuclei; soon to be separated - make 2 cells Describe appearance of Golgi Body under a microscope 1. Stacks of cisternae (flattened stacks) 2. Cisternae are flattened and curved 3. Cisternae are different sizes 4. Smooth membranes/no ribosomes (unlike RER) 5. There is presence of vesicles Describe protein transport (from Ribosome to Golgi) 1. Protein made at ribosomes (after translation of mRNA) 2. Ribosomes are attached to the RER 3. The protein is then stored within RER 4. Proteins are folded and assume their final 3D shape 5. RER package the proteins into membrane bound vesicles 6. Vesicles move to Golgi and fuse with Golgi apparatus 7. Golgi modifies the protein (e.g. add carbohydrate to make glycoprot.) 8. Water is removed (to concentrate) 9. Golgi produces vesicles; which can be used to secrete the protein Describe how fertilised egg can be used as a source of pluripotent stem cells. 1. Fertilised egg allowed to grow (for a few days/divide several times) 2. Forms a blastocyst; a hollow ball of cells 3. The cells in the inner cell masses are pluripotent 4. The cells are extracted 5. Fertilised egg from IVF; discarded after use Fertilisation of plant 1. Pollen grain lands on style and pollen tube grows down style 2. Pollen tube grows towards the ovary; down the style 3. Digestive enzymes secreted; digest style tissue; aids pollen tube growth 4. The pollen tube transports tube nucleus & generative nucleus 5. Once it reaches embryo sac, tube nucleus bursts 6. Generative nucleus divides via mitosis to form two male nuclei 7. One male nuclei fuses with female gamete to form diploid zygote 8. Other fuses w/ two polar NUCLEI to form triploid endosperm nucleus Describe appearance of chloroplast (instead of RER) 1. Ribosomes floating within membrane - RER has ribosomes attached 2. It has DNA; ribosome does not contain DNA 3. Presence of internal membranes e.g. thylakoid membrane, grana 4. It has double nucleus membrane; RER does not have double nuc. mem. 5. No flattened sacs/cisternae & contains starch How Sperm is adapted to its function 1. Streamlined - reduced resistance 2. Acrosome containing enzyme - involved in digestion of zona pellucida 3. Haploid nucleus - allow restoration of dip. chromosomes at fertilisation 4. Large number of mitochondria - to supply ATP/energy for movement 5. Flagellum present - for propulsion/swimming
Explain what is meant by diploid 1. A cell which has half the number of chromosomes found in a body cell 2. It contains only one chromosome from each homologous pair 3. Diploid nucleus found in gametes; nucleus is an organelle Describe protein transport 1. Amino acids transported to RER via (tRNA attaches to one each) 2. At ribosomes, amino acids line up and join via peptide bonds 3. The protein is then folded into its 3D/tertiary shape in the rER 4. It is then packaged into membrane bound vesicles at the end of the rER 5. The vesicle moves towards and then fuses with the Golgi apparatus 6. Golgi apparatus modifies the protein; adds carb to make glycoprotein 7. Vesicles move to cell membrane and secret enzyme via exocytosis Why Xylem Tissue cannot be used in plant tissue culture 1. Xylem tissue is dead & has no genetic material 2. It is not totipotent; as it is already differentiated 3. Therefore, it is unable to divide via mitosis Why use cling film with plant tissue culture experiment 1. To prevent the bacteria (e.g. airborne) from contamination/entering 2. Grow rapidly with help of growth hormone; reduce explant growth 3. Harmful to humans (pathogenic) or will compete with plant for nutrient 4. Maintain humidity conditions; allow sunshine to go through 5. Use sterilisation to kill microbes Define Tissue - group of similar cells that work together to carry out a specific func. Conditions of a seedbank to ensure long term conservation 1. Test viability at regular interval; if viability decreases collect new seeds 2. Surface sterilisation of seeds 3. Only store seeds with a living embryo 4. Dry seeds - reduce effect of freezing temp 5. Cool/Cold - inhibit germination, reduce enzyme activity, prolong decay Describe and Explain what is meant by a Double Blind Test 1. Tested on two groups of patients; each group given drug or placebo 2. Placebo used as control w/ drug (e.g comparison) (e.g. sugar pill) 3. Placebo gives psychological effect; patients believe they will get better 4. Neither tester/doctor nor patient know which group is given placebo 5. This removes bias; used to see effectiveness of drug Fertilisation of male nuclei in plants 1. Generative nucleus divides to form two male gametes; via mitosis 2. Pollen tube fuses w/ embryo sac; double fertilisation occurs 3. One male gamete fuses w female gamete to form diploid zygote 4. Other male gamete fuses w two polar nuclei to form triploid endosperm How genetic variation occurs in meiosis 1. Ref. to both independent assortment and crossing over 2. I.A. gives rise to new combo of paternal/maternal chromosomes 3. Crossing over involves swapping of sections of chromatids 4. Produces recombinants/different or new combinations of alleles How scientists can publish their findings 1. Scientific journal 2. At a conference What happens after findings are published? 1. Peer review - check for any plagiarism, check if conclusions are valid 2. Repeat experiments to confirm/validate findings Molecular Phylogeny 1. Phylogeny describes evolutionary relationship (between organisms) 2. Molecular phylogeny looks at similarities/diff. based on DNA seq./cells 3. Using evidence via DNA profiling, looks at sequence of bases/a.a 4. Taxonomic groups have diff. similarities and differences 5. Organisms w/ more features in common are placed in a group What happens after acrosome reaction to prevent polyspermy 1. Sperm cell fuses w egg cell membrane; triggers cortical reaction 2. Cortical granules fuse w/ egg cell membrane & released via exocytosis 3. Contents of cortical granules released into jelly layer; thickens layer Maintaining the genetic diversity via breeding programs 1. Captive breeding will increase population of species 2. No. of individuals is small/small gene pool compared to wild 3. Studbooks kept, Inter-zoo exchange of animals for breeding 4. Zoos select mates of species - prevent inbreeding & avoid genetic drift 5. Introduce alleles from other populations - encourage outbreeding 6. Use of artificial insemination and IVF 7. Measure the genetic diversity via DNA profiling How to tell Eukaryotic cell from Prokaryotic (bacterial cell) 1. Presence of membrane bound organelles only in eukaryotic 2. Absence of slime capsules and plasmids suggest eukaryotic 3. Ribosomes larger in eukaryotes 4. DNA in nucleus in eukaryotes 5. DNA is LINEAR in eukaryotes and circular in bacteria/prokaryotes Describe structure of cellulose in plant cells 1. Made up by beta-glucose monomers 2. Joined by 1,4 glycosidic bonds (formed via condensation) 3. Cellulose molecules linked by hydrogen bonds to form microfibrils 4. Microfibrils arranged in a mesh/layers; give plant strength & flexibility Describe the xylem tissue structure 1. Made up of hollow dead cells that are joined end to end - no end walls 2. There is thickened cell walls and presence of lignin to support plant
How breeding programs and reintroduction schemes help increase pop. in wild 1. Advantageous alleles that are adapted to change are passed to offspring 2. This increases the no. of species that are immune to disease etc 3. Use IVF or AI to increase the number of offspring 4. Reintroduction to the wild; increases allele freq. in the wild population How cell cycle is involved in plant growth 1. Increases the number of cells 2. Increases the size of cells during growth phase 3. Cells are made via mitosis/cell division (produce daughter cells) Magnesium 1. Used for production of chlorophyll; found in chloroplast 2. Chloroplast used for photosynthesis - produce energy for plant 3. Increase in photosynthesis leads to increased yield - more growth Nitrate 1. Nitrate used in production of amino acids, protein and DNA
2. Amino acids used to make proteins; more protein - increase growth How cell wall is strong and flexible 1. Cellulose microfibrils arranged parallel to one another in layers 2. Cellulose molecules joined via H bonds to form microfibrils 3. Microfibrils in second cell wall are in mesh/criss cross Phenotype - result of an interaction between the genotype and the environment Why mitosis leads to little genetic variation 1. Low genetic diversity due to a low number of diff. alleles in gene pool 2. Asexual reproduction leads to offspring genetically identical to parent 3. No meiosis/no recombination & no new combos of m/p chromosomes 4. Variation only possible as a result of mutation (very rare) Mineral Deficiency Experiments 1. Minimum 5 difference nitrate ion concentrations 2. Repeat at each concentration 3. Measure dependent variable; e.g. increase in length/mass 4. Use plants that are genetically similar - same age, from same plant 5. Control temp, light intensity, water provided, pH of solution 6. Control - with no nitrate Feature
Prokaryotic Cell
Animal Cell (Eu)
Plant Cell (Eu)
Nuc. w/ envelope
No
Yes
Yes
Membrane-bound organelles
No
Yes
Yes
DNA found as..
In a loop
Separate strands
Separate strands
Slime capsule
Somtimes
No
No
Flagella
Simple
Complex
No
Cell wall
Yes - bacterial
No
Yes - cellulose
Size of cell
Small
Medium
Large
Feature
Animal Cell
Plant Cell
Cellulose Cell Wall
NO
YES
Plasmodesmata
NO
YES
Pit
NO
YES
Chloroplast
NO
YES
Sap Vacuole/Tono
NO
YES
Cell Membrane
YES
YES
Mitochondria
YES
YES
Ribosomes
YES
YES
RER
YES
YES
SER
YES
YES
Golgi Body
YES
YES
Nucleus
YES
YES
Nucleolus
YES
YES
Centrioles
YES
NO
