Multiple choice questions, please circle the best answer.

1. Which statement BEST describes the fate of propionyl-CoA in mammalian systems?

a. Propionyl-CoA is metabolized via a reaction sequence that involves vitamin B12 and biotin.
b. Propionyl-CoA is converted to acetyl CoA.
c. Propionyl-CoA and acetyl CoA condense to form a 5 carbon precursor of a TCA cycle intermediate.
d. Propionyl-CoA is oxidized to malonate and CoA.
e. The methyl group of propionyl-CoA is transferred to S-adenosylhomocysteine to form s-adenosylmethionine.

2. Which of the following is elevated in plasma immediately after eating?

a. lactate
b. glucagon
c. free fatty acids
d. chylomicrons
e. acetoacetate

3. Which of the following statements is correct for the well fed (just ate dinner) state?

a. acetyl-CoA is elevated
b. the levels of hepatic fructose-2,6 bisphosphate are elevated
c. lactate is elevated
d. phosphorylase a is not phosphorylated
e. cAMP levels are elevated

4. Place the following four types of fuel in order of increasing oxidation state (most oxidized on the right).

a. glucose>amino acids>ethanol>fats
b. amino acids>glucose>fats>ethanol
c. fats>amino acids>ethanol>glucose
d. fats>glucose>ethanol> amino acids

5. How many moles of ATP can be made from the complete oxidation of palmitoate?

a. 131
b. 35
c. 96
d. 129
e. none of the above

6. Which of the following statements is correct?

a. The two nitrogen atoms that are incorporated into urea enter the cycle as ammonia and alanine.
b. Urea is produced directly by the hydrolysis of ornithine.
c. ATP is required for the reaction in which argininosuccinate is cleaved to form arginine.
d. The urea cycle occurs exclusively in the cytosol.
e. In humans, the major route of nitrogen metabolism from amino acids to urea is
catalyzed by the combined actions of transaminase (aminotransferase) and glutamate dehydrogenase.

7. Which of the following statements about the synthesis of carbamoyl phosphate
by carbamoyl phosphate synthetase I is incorrect?

a. The enzyme catalyzes the rate-limiting reaction in the urea cycle.
b. The reaction is allosterically activated by N-acetylglutamate.
c. The reaction is reversible.
d. The enzyme incorporates CO₂ into carbamoyl phosphate.
e. The reaction requires two high energy phosphates for each carbamoyl phosphate molecule synthesized.

Short answer/essay questions

1. Explain why fatty acids with an even number of carbons can not be used to synthesize glucose and fatty acids with an odd number of carbons can be used to make glucose.

2. The Cori cycle is involved in recycling the carbons in pyruvate and these carbons end up in glucose.

a. Explain the cycle, designating the tissues where the reactions occur.

b. Explain how the Cori cycle exacerbates the hyperglycemic state in a diabetic patient.

3. Palmitoate that is uniformly labelled with tritium was oxidized in liver mitochondrial cells. The amount of radioactivity in the isolated product (acetic acid, which was derived from acetyl CoA) contained only a small percentage of the original radioactivity (1/24).

a. Give the reactions involved in fatty acid metabolism to acetyl-CoA.

b. Where did the rest of the radioactivity go?

4. Alanine and lactate have similar structures as shown below. How many moles of ATP can be generated from the complete oxidation of a mole of lactate? of a mole a alanine? Explain the reactions that generate the ATP (in general terms, no structures are required).

5. Fill in the table below

Fill in the table below

Medical Condition	Defective enzyme or protein	Toxic metabolite and/or effects
degradation of leu, ile, val	Methylmalonyl-CoA mutase
Phenylketonuria
Leber's optic neuropathy	Mitochondrial complex I protein

6. The energy for the synthesis of ATP in the mitochondria comes from the pH gradient that exists across the inner mitochondrial membrane. If the pH of the mitochondrial matrix is 7.7 and the pH of the inner membrane space is 7.2, what is the G for the flow of protons into the matrix? (Ignore the contribution of the electronic potential across the membrane.)

7. Many sea mammals drink no water, and have diets that are high in fat. In addition to using stored fat for insulation, they also use fat stores as a source of water. How many kg of water can be obtained from the complete metabolism of 1.1 lbs of tripalmitoylglycerol?

8. Runner Ron did some deep and rapid breathing right before his BIG 400 meter sprint race. Immediately after the race, his blood contained high levels of lactate, and then these levels decreased to normal levels about 40 minutes after the race.

a. Why did he do the deep and rapid breathing?

b. Why did the lactate levels increase and what tissue(s) generated the lactate?

c. Where did the lactate go? Be specific and indicate tissue type and show structures.

d. What would happen to a runner's lactate levels immediately after a sprint and 40 minutes after a sprint, if the runner was diabetic?

9. Pick one of the following questions:

a. Would 2,4 dinitrophenol or atractyloside affect the ATP concentration of erythrocytes? Explain your answer.

b. Why would it be inadvisable to treat snake bite victims with valinomycin? Explain your answer.

c. What kinds of enzymes are found in peroxisomes? Do these organelles have a respiratory chain that is similar to that found in mitochondria?

d. Why would a patient with a deficiency in the glycogen branching enzyme have excess lactate, pyruvate and free fatty acids in their blood?