Investigation of the effect of temperature change on the rate of respiration in yeast
Background information Cellular respiration is the process by which cells are able to b reak down glucose to release energy. energy. There are two types ty pes of process in which cellular respiration occurs. It can either be in the presence of oxygen (Aerobic respiration) or in the absence of oxygen (anaerobic respiration) in which both will result in different products. When oxygen is present, yeast cells use enzymes to convert glucose to carbon dioxide, water w ater and release (more) energy. energy. When yeast cells respire without oxygen they use enzymes to convert glucose to ethanol(fermentation), carbon dioxide and release (less) energy. energy. (Author Unknown, “ Does temperature change affect the respiration of yeast ?”) Aerobic respiration: C6H12O6 + 6O2 ! 6CO2 + 6H20 +ATP Glucose + oxygen
carbon dioxide + water + energy
!
Anaerobic respiration: C6H12O6
!
Glucose
!
C2H5OH + 2CO2 + ATP
Ethanol + carbon dioxide + energy
Aim To investigate the effect of temperature (of 36°C, 40°C and 60°C) on the rate of respiration in yeast
Variables Variables
Dependent:-
How it will be manipulated
Rate of respiration:Foam height in cm
Independent:- The changing temperature of the water bath Restrict the amount of air that the yeast has to work with
The level of foam that is produced will be measured by using a ruler and a marker. This will be done by measuring from the top of the water to the top of the foam. By comparing the heights of the foam, we would be able to conclude the relative rate of respiration for the temperature 36°C, 40°C and 60°C By setting up 3 different water baths to the specified temperature needed for the experiment, which is 36°C, 40°C and 60°C For the temperature (36°C) 3 of the test-tube will be covered with cling wrap on top of the opening to restrict the amount of air into the test-tube.
Controlled:-
Same amount of yeast and sugar
This will be controlled by using an electronic balance to measure the weight of yeast and sugar. For all the trials each will have the same amount of sugar (1g) and yeast (2g).
Same volume of water
The volume of water will be controlled by using a measuring cylinder. Each trials will have 20ml of water. A pipette can be used to control precisely or distribute a precise amount of water.
Same amount of time for each trials
The amount of time for the trails will be controlled by using a stopwatch. The readings will be taken at the same time. The height of foam will be measured every 5 minutes for 10 minutes total.
Same test-tube size By selecting the same size of test-tube that is present in the lab.
Hypothesis As the temperature increases, rate of respiration increases, therefore forming a greater amount of foam as more carbon dioxide will b e released by yeast. However if the temperature is above the optimum temperature the rate of respiration will decrease thus less amount of foam is produced. ("The Effect of Temperature on the Rate of Respiration in Yeast." 123HelpMe.com) This will happen because as temperature rises the rate of respiration increases as enzymes in yeast will move faster and with more energy, thus the molecules have a greater chance to collide and react. However if the reaction temperature is too high or is above the optimum temperature, enzyme will denature and this will decrease the rate of respiration. (“Temperature, pH and enzymes”, BBC.co.uk) Moreover the test-tube which will be covered by cling wrap will produce much less than the one which isn't covered at the same temperature because when oxygen is presence more energy is released.
Equipment list I.
Dried Yeast (24 grams)
II.
Sugar (12 grams)
III. Water (240ml) IV.
Water bath (3)
V.
Stopwatch
VI. Small test tube (12) VII. Test tube (12) VIII. Plastic test-tube rack (3) IX. Measuring cylinder
X.
Plastic funnel
XI. Waterproof marker XII. Ruler XIII. Spatula XIV. Petri dish XV. Electronic balance XVI. Pipette XVII.Cling wrap
Method 1.
Gather all the apparatus needed to start the experiment
2.
Set up each water baths to different temperatures (36°C,40°C and 60°C)
3.
Using a measuring cylinder; measure 20ml of water for 12 test-tube (each containing 20ml of water) Pipette can be used to make it easier to distribute a pr ecise amount of water.
4.
Use the test-tube rack to hold the test-tubes
5.
Use a petri dish to hold the yeast/sugar to measure the weight by using an electronic balance
6.
By the help of a spatula, add to the petri dish 2g of yeast and repeat this 12 times to add for each small test-tube
7.
Use a funnel to channel the yeast in the small test-tubes (12) in order to avoid/ reduce losing yeast when poring it into the small test-tube
8.
Measure 1g of sugar using the same steps from 6 to 8 and add to each test-tube containing the yeast 1 gram of sugar. Therefore each of the 12 small test-tube will contain 2g of yeast and 1g of sugar.
9.
Use the test-tube rack to hold the test-tubes
10. Separate each test-tubes in 4 sets of 3. Label the test-tube which contains water (by using a waterproof marker) as A,B and C and mark the original water level. 11. Use the test-tube rack to hold the different sets of test-tube. One test-tube rack will contain 12 test tubes (6 test-tube of water and 6 test-tube of yeast and sugar) as it will be tested for the temperature of 36°c 12. Deposit the 3 test tube racks (The test-tube containing water) in the different temperatures; 36°c, 40°c, 60°c in the water bath and let it sit for 5 minutes
Example of how to proceed for the experiment. Temperature 60°c with 3 test-tube containing water (Repeat those steps for the other temperatures) 13. After 5 minutes add simultaneously in each test-tube the sugar and yeast. 14. Let it sit for 5 minutes then measure the level of foam that was formed in the testtube. The height of foam will be measured every 5 minutes for 10 minutes total. 15. Remove the test tube rack from the water bath and measure the distance from the original marking to the new markings by using a ruler. 16. Record the findings in a tabular form Temperature- 36°c
- For the temperature of 36°c it will have the same method as 13-16, however 3 of the test-tube will be covered by cling wrap. Example of the table to record findings Temperature
Trial
36°c (Uncovered)
A
After 5 minutes
After 10 minutes
B C 36°c (Covered)
A B C
Safety procedure ! !
Be careful while handling the test tubes into the water bath as it can be very hot Do not directly touch the water inside the water bath- Use a rack to put the test tubes into the water bath
Results from the experiment done in class the 8/03/16 Temperature
Trial
36°c (Covered)
36°c (Uncovered)
40°c
60°c
Level of foam (cm) after 5 minutes
level of foam (cm) after 10 minutes
Average
Change from the 1st to 2nd reading
5.7
3.4
A
5.9
9.3
B
7.4
14
6.6
C
5.0
12
7.0
A
10.9
(N/A)
B
11
(N/A)
"
C
13
(N/A)
"
A
4.5
8.8
B
2.3
4.4
2.1
C
3.8
5.7
1.9
A
2.2
3.5
B
1.6
2.1
0.5
C
3.1
5.6
2.5
11.7
2.8
1.4
"
4.3
1.3
Diagram: The average rate of respiration in yeast The average level of foam produced in 10 minutes (CO2 released) 12
) m c ( m a o f f o t h g i e H
9
6
3
0 36°c (covered)
36°c (Uncovered)
Temperature (°c)
40°c
60°c
Explanation of results The graph above shows the average rate of respiration in yeast for different temperatures36°c, 40°c and 60°c. The lowest amount of foam formed is at temp erate 60°c with an average of 1.4cm and the highest is at temperate 36°c with a height of 11.7cm. We notice that the level of foam decreases as the temperature increase to 60°c. There is a dr astic change in height of foam as it went from 11.7cm (36°c) to 2.8cm (40°c) , which is 8.9cm of difference. Therefore we can conclude that the optimum temperature was reached between 36°c to 40°c as the rate of respiration decreased due to the enzymes denaturing. Furthermore we can conclude that the rate of respiration wor ks best at body temperature which is around 37°c. The test-tube that was covered with cling wrap p roduced 5.7cm of foam which is 6cm lower than the test-tube which was uncovered at the same temperature. Thus it can be concluded that yeast respire best aerobically (with oxygen) than anaerobically (without oxygen) as the rate of respiration is higher with oxygen than without oxygen.
Evaluation and validity of hypothesis In conclusion, my hypothesis was supported to some extent because according to the result as the temperature reached above the optimum temperature the rate of respiration decreased as the temperature increased. However the results are not as conclusive to support fully my hypothesis as I predicted that “As the temperature increases, rate of respiration increases”. From the results it could be seen that the optimum temperature was between 36°c to 40°c. Therefore it is not possible to conclude whether the yeast respires more rapidly at higher temperatures than at lower temperatures as we did not test for lower temperatures. However my hypothesis concerning the test-tubes that are covered is valid as the heights of foam is 6cm less than the test-tube which is uncovered.
Validity of method based on the results The method is either right or wrong as the results was not as conclusive but it was as I predicted. The results does show that as the temperature reaches above the optimum temperature the rate of respiration decreases as temperature increases. However, because we did not test for a lower temperature than 36°c I am unable to conclude whether my hypothesis is right as according to the results it is not possible to conclude whether the rate of respiration increases as temperature increases. However I think the procedures during the experiment was done right and doing 3 trials for each temperature enabled us to make an average, which helps to have a better result that is more precise and accurate.
Limitation/ errors
- Not enough of temperatures to make a conclusive validation of the hypothesis. - We did not mix the yeast and glucose mixture in the water. This may have biased the -
results as it could be seen that some glucose and yeast was stuck on the side of the glass or it was not properly mixed into the water. For the temperature 36°c which was uncovered, we were unable to measure the height of foam in the 2nd reading as the foam exceeded the test-tube.
Improvement or extensions to the method - More temperatures for testing the rate of respiration in yeast. I.e. testing for a much lower -
temperature like 0°c, 15°c, 20°c and so on. This would be more conclusive for the investigation of the e #ect of temperature on rate of respiration in yeast. Use a spatula to mix the yeast and sugar in the water in order to avoid the mixture of yeast and sugar to be stuck to the test-tube glass thus making it a fair reaction test Rather than using a test-tube use a graduated cylinder as it is bigger, longer and it has measurement, which makes it easier to measure the height of foam and avoid the foam to exceed faster than in a test-tube
References • •
• •
"The Effect of Temperature on Yeast Respiration." 123HelpMe.com. 11 Mar 2016 . “Does temperature change affect the respiration of yeast?” https://vle.stvincent.ac.uk/ 2014/pluginfile.php/33446/mod_resource/content/2/Does-temperature-change-affect-therespiration-of-yeast-10vsrbd%20(1).pdf. 11 March 2016 ouLearn on YouTube, “Yeast Experiment: measuring respiration in yeast”. https:// www.youtube.com/watch?v=Cngt2HmJuSo 11 march 2016 “Temperature, pH and enzymes.” http://www.bbc.co.uk/schools/gcsebitesize/science/ add_aqa/proteins/proteinsrev3.shtml 11 march 2016
