Attach graph to Lab Report.
1. During this experiment, gas pressure was measured. By what process was the gas produced?
___________________________________ Which gas was it? _____________________________________
2. Yeast was added to all the tubes, but not all of them produced the gas. What had to be
present in order for the gas to be made? ____________________________________________________
3. This experiment was run at approximately 45
C. When performed at room temperature (24C),
little if any gas would have been produced within the 15-minute sampling time. Why? (Hint:
Refer back to Lab 9 on Enzymes.) ___________________________________________________________
__________________________________________________________________________________________
4. What was the purpose of layering the oil on top of the solutions in all 6 tubes? __________________
__________________________________________________________________________________________
5. Considering the contents of tube 1, explain why it is the negative control for this experiment.
__________________________________________________________________________________________
6. Study the line on the graph for tube 2. Note that it increased steadily. However, at some point
it will level off. Offer an explanation as to why. ______________________________________________
__________________________________________________________________________________________
7. Compare the amount of gas produced in tube 3 to that of tube 2. How does the concentration
of glucose affect the rate of fermentation? _________________________________________________
__________________________________________________________________________________________
Table 1: Results.
test tube rate (kPa/min)
(record to 2
decimal places)
1: 0% glucose
2: 1% glucose
3: 5% glucose
4: 5% galactose
5: 5% glucose + NaF
_____6: 5% glucose + KCN
_____
96 Lab 10: Alcohol Fermentation
8. Compare the amount of gas produced in tube 4 to that of tube 3. Galactose is an isomer of
glucose. Are the yeast enzymes able to metabolize galactose as they do glucose? ___________
Considering enzyme specificity, explain these results. ________________________________________
__________________________________________________________________________________________
9. NaF is the enzyme inhibitor in tube 5.
a. Did any fermentation occur in test tube 5? ______________________________________________
b. Because NaF blocks the last enzyme of glycolysis, what end product of glycolysis is not
produced when NaF is present?________________________________________________________
c. Why does the lack of this end product stop fermentation? ________________________________
_______________________________________________________________________________________
d. Does NaF inhibit enzymes located in the cytoplasm or the mitochondria? __________________
10. KCN is the enzyme inhibitor in tube 6.
a. Since KCN is an enzyme inhibitor, why was there gas production in this tube? ______________
_______________________________________________________________________________________
b. Does KCN inhibit enzymes located in the cytoplasm or the mitochondria? _________________
c. Compare the slopes for tubes 3 and 6. Explain why they are very similar. ___________________
_______________________________________________________________________________________
11. Fermentation does not produce any ATP. So, what is its value to the yeast? ___________________
__________________________________________________________________________________________
__________________________________________________________________________________________
12. Why is this type of fermentation called alcohol fermentation? (Be specific.) ___________________
13. Refer to Figure 1 to answer the following questions.
a. The initial substrate, ___________________, has _______ carbons.
b. The final product of alcohol fermentation is two molecules of ________________ with a total
of ______ carbons.
c. What happened to the “missing” carbons? ______________________________________________
14. Give 2 potential sources of error in this experiment. _