BIOCHEMISTRY 4613/6613

Exam 3 - March 17, 2000

Row number: Name:

SHORT ANSWER:

1. List in proper sequence the individual components of the electron transport system. (10 points)

2. Describe using a simple illustration and a few words the chemiosmotic model of how the electron transport system operates during oxidative phosphorylation. (15 points)

3. Which of the following scientists developed the chemiosmotic model to explain how the electron transport system operates? (3 points)

a. David Green

b. Albert Lehninger

c. Peter Mitchell

4. Consider a liver cell carrying out the oxidation of glucose under aerobic conditions. Compare the effects of adding a site specific inhibitor such as cyanide and an uncoupling agent such as DNP on each of the following conditions. Indicate whether each statement would be true or false for each inhibitor indicated. (12 points)

a. ATP production in the cell would drop to zero. Cyanide DNP

b. ATP production by oxidative phosphorylation would drop to zero. Cyanide

DNP

c. The rate of glucose consumption by the cell would decrease sharply. Cyanide

DNP

d. The rate of oxygen consumption would increase. Cyanide DNP

e. The TCA cycle would speed up to compensate. Cyanide DNP

f. The cell would switch to fatty acid oxidation as an alternative to glucose oxidation in an attempt to make ATP. Cyanide DNP

5. If one glucose molecule is converted to carbon dioxide and water in a normal liver cell and the NADH produced during glycolysis is transported into the mitochondria via the glycerol-3-phosphate shuttle, the total potential ATP yield would be , whereas if the NADH was transported via the malate-aspartate shuttle, the ATP yield would be . (4 points)

6. The role of hormone-sensitive triacylglycerol lipase is to: (3 points)

a. hydrolyze triacylglycerols in adipose tissue

b. hydrolyze triacylglycerols in the intestine

c. hydrolyze triacylglycerols in capillaries

7. Calculate the net ATP yield for the complete oxidation of an 18 carbon saturated fatty acid by beta-oxidation and the TCA cycle. Assume that all energy-conserving products are used for ATP synthesis in the mitochondria. (3 points)

8. The synthesis of fatty acids and their breakdown by beta-oxidation occurs by separate pathways. Compare the two pathways by filling in the blanks below: (16 points)

beta-oxidation fatty acid synthesis

Cellular location

Acyl group carrier

Coenzyme(s) required

Carbon unit involved

9. Acetyl groups are transported across the mitochondrial membrane for fatty acid synthesis in the form of: (3 points)

a. acyl carrier protein

b. citrate

c. acetyl-carnitine

10. Palmitic acid is transported across the mitochondrial membrane for beta-oxidation in the form of: (3 points)

a. palmitoyl-acyl carrier protein

b. palmitoyl-CoA

c. palmitoyl-carnitine

11. Beta-oxidation of fatty acids serves as a major energy source for the following tissue whereas fatty acid synthesis occurs mainly in the following tissue . (6 points)

12. Name the three compounds that are referred to as ketone bodies. (9 points)

13. Briefly explain a metabolic condition which would result in ketone body synthesis. (4 points)

14. Ketone bodies are normally used as a source of energy by the following tissue .

(3 points)

15. Fatty acid synthesis and beta-oxidation are either stimulated or inhibited by certain hormones. For each hormone listed below, indicate whether it stimulates or inhibits fatty acid synthesis. (6 points)

Hormone Fatty acid synthesis

Insulin

Glucagon

Epinephrine