Quiz 5, BICH 410 (MWF3-3:50), Friday, Nov. 13, 1998

Clearly circle the letter corresponding to your answer for each problem. There are six problems, four of which count 3 points, and two for 4 points. No partial credit given for multiple-choice questions.

1. Which of these enzymes is a control point, regulated by the cell's energy supply?
Answer: D; all can be regulated allosterically by ATP

2. The ultimate electron acceptor in the fermentation of glucose to ethanol is:
Answer: C; in reaction catalyzed by alcohol dehydrogenase, electrons from NADH are used to reduce acetaldehyde to ethanol; acetaldehyde is the ultimate electron acceptor

3. Glucokinase:
Answer: B; catalyzes reaction: glucose + ATP -> glucose-6-phosphate + ADP

4. Galactosemia is a genetic error of metabolism associated with:
Answer: A

5. (4 pts) The conversion of one mole of glucose-6-phosphate to two moles of lactate in glycolysis is accompanied by a net gain of:
Answer: C; Starting with glucose-6-phosphate, there is one ATP used (at the phosphofructokinase reaction) and 2 X 1 ATP produced at phosphoglycerate kinase, and 2 X 1 ATP produced at pyruvate kinase; net ATP change = -1 + 2 + 2 = 3; there is no net change in NADH in this fermentation

6. (4 pts) If glucose molecules labeled with 14C in C-1 were fed to yeast carrying out ethanol fermentation, where would the 14C label be in the products?
Answer: A; see solution to Problem 5, Chap. 13 to help in following carbon atoms through glycolysis; C-1 carbon is carbon carrying phosphate in DHAP and number 3 carbon in glyceraldyde-3-phosphate; this carbon becomes the methyl carbon in pyruvate and the methyl carbon in ethanol (C-2 of ethanol; you should remember how these are numbered from Organic Chemistry!)