BIOCHEMISTRY 4613/6613

Exam 2 - February 18, 2000

Row number: Name:

Matching: Match the correct allosteric modifier listed with the metabolic condition given. (2 points each).

Metabolic condition Allosteric modifier

1. An inhibitor of phosphofructokinase                         a. AMP

2. An inhibitor of pyruvate kinase                                b. ADP

3. An activator of phosphofructokinase                        c. ATP

4. An inhibitor of hexokinase                                       d. citrate

5. An inhibitor of citrate synthase                                 e. acetyl CoA

6. An activator of pyruvate dehydrogenase                  f. Ca++

7. An inhibitor of isocitrate dehydrogenase                  g. NAD+

8. An activator of pyruvate carboxylase                      h. NADH

9. An activator of citrate synthase                               i. glucose 6 phosphate

10. An activator of phosphorylase b

Reactions: Give the name of the substrate(s), product(s) and coenzyme(s) for each of the following enzymes. Also indicate if the reaction is reversible or not. No structures necessary.

11. Pyruvate dehydrogenase (10 points)

12. Citrate synthase (10 points)

13. Succinyl CoA synthetase (8 points)

14. Malate dehydrogenase (8 points)

15. Glucose 6 phosphatase (6 points)

Short Answer:

16. Indicate which of the following vitamins serve as the precursor of coenzyme A. (2 points)

biotin, lipoic acid, pantothenic acid or thiamin

17. Indicate which of the following type reactions usually require biotin as a coenzyme. (2 points)

CO2 fixation or decarboxylation

18. Give the net ATP yield (from both substrate level and oxidative phosphorylation) for each of the following conversions: (2 points each)

a. acetyl CoA -----> CO2 + H2O

b. pyruvate -----> CO2 + H2O

c. free glucose -----> CO2 + H2O

d. glucose from glycogen -----> CO2 + H2O

19. Briefly explain how each of the following is involved in carbohydrate metabolism. (2 points each)

a. Glucagon

b. Epinephrine

c. Insulin

d. Glycogenin

e. cAMP

20. Illustrate the Cori cycle and briefly describe its importance or function. (10 points)

21. Briefly explain why plants can convert stored fat or lipid to carbohydrate for germination whereas animals cannot convert fat to glucose during gluconeogenesis. (6 points)