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
- A) glycogen phosphorylase
- B) phosphofructokinase-1
- C) pyruvate kinase
- D) All of the above are control points.
- E) None of the above is a control point.
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
- A) pyruvate
- B) acetate
- C) acetaldehyde
- D) ethanol
- E) lactate
Answer: B; catalyzes reaction: glucose + ATP -> glucose-6-phosphate + ADP
- A) acts in the conversion of liver glycogen to glucose-1-phosphate.
- B) is a hexokinase isozyme found in the liver.
- C) is found in all mammalian tissues.
- D) converts glucose-6-phosphate to fructose-6-phosphate
- E) catalyzes a substrate level phosphorylation of ADP.
4. Galactosemia is a genetic error of metabolism associated with:
- A) deficiency of UDP-glucose:galactose-1-phosphate uridylyltransferase.
- B) inability to digest lactose.
- C) excessive ingestion of galactose.
- D) deficiency of aldolase B.
- E) deficiency of phosphoglucomutase.
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
- A) one mole of ATP.
- B) two moles of ATP.
- C) three moles of ATP.
- D) four moles of ATP
- E) one mole of NADH
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!)
- A) C-2 (methyl group) of ethanol
- B) C-1 of ethanol only
- C) CO2 only
- D) C-2 of ethanol and CO2
- E) C-1 of ethanol and CO2