Q: Which of the following best describes the overall reaction of the Citric Acid Cycle?

$\text{Acetyl-CoA} + 3\ NAD^+ + FAD + GDP + P_i + 2\ H_2O \rightarrow 2\ CO_2 + 3\ NADH + 3\ H^+ + FADH_2 + GTP + CoA$

Question 1

Which of the following is NOT a function of the pyruvate dehydrogenase complex?

Accepted Answer

It generates both NADH and FADH$_2$ for the electron transport chain.

Question 2

If glucose labeled at the first and fourth carbons with $^{14}$C is converted to pyruvate by glycolysis and then to acetyl-CoA, where will the $^{14}$C label appear in the acetyl-CoA molecule?

Accepted Answer

In the methyl group of acetyl-CoA

Question 3

Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to respiring mitochondria, which molecule would you expect to decrease in concentration?

Accepted Answer

Fumarate

Question 4

Which of the following is NOT an intermediate in the Citric Acid Cycle?

Accepted Answer

Acetyl-CoA

Question 5

If oxaloacetate uniformly labeled with $^{14}$C at all carbons is added to mitochondria with an adequate supply of acetyl-CoA (unlabeled), after one turn of the cycle, how much radioactivity will remain in oxaloacetate?

Accepted Answer

50\%

Question 6

Which enzyme catalyzes the only substrate-level phosphorylation in the Citric Acid Cycle?

Accepted Answer

Succinate thiokinase (succinyl-CoA synthetase)

Question 7

A patient has a mutation that inactivates the enzyme alpha-ketoglutarate dehydrogenase. Which of the following would you expect to accumulate?

Accepted Answer

Alpha-ketoglutarate

Question 8

Which of the following steps in the Citric Acid Cycle directly produces NADH?

Accepted Answer

$\alpha$-ketoglutarate to succinyl-CoA

Question 9

Which molecule is regenerated at the end of the Citric Acid Cycle to combine with acetyl-CoA and begin the cycle again?

Accepted Answer

Oxaloacetate

Question 10

Which of the following best describes the overall reaction of the Citric Acid Cycle?

Accepted Answer

$	ext{Acetyl-CoA} + 3\ NAD^+ + FAD + GDP + P_i + 2\ H_2O ightarrow 2\ CO_2 + 3\ NADH + 3\ H^+ + FADH_2 + GTP + CoA$

Citric Acid Cycle: Practice Questions and Key Concepts

Study Guide - Practice Questions

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