Q: Which of the following equations correctly represents the overall carbon change during the conversion of pyruvate to acetyl-CoA?

$$\text{Pyruvate (3C)} \rightarrow \text{Acetyl-CoA (2C)} + \text{CO}_2$$

Q: Why is the citric acid cycle considered part of aerobic metabolism even though it does not directly consume $$\text{O}_2$$?

Because the regeneration of $$\text{NAD}^+$$ and $$\text{FAD}$$ depends on the electron transport chain, which uses $$\text{O}_2 as $$the final electron acceptor.

Q: Which of the following best describes the fate of the two carbon atoms from acetyl-CoA during one turn of the citric acid cycle?

They enter the cycle and are eventually released as $$\text{CO}_2$$, but not necessarily in the same turn.

Q: Which of the following best summarizes the products generated from one molecule of glucose after two turns of the citric acid cycle?

$$6 \ \text{NADH}, \ 2 \ \text{FADH}_2, \ 2 \ \text{GTP}, \ 4 \ \text{CO}_2$$

Question 1

Which of the following best explains why the citric acid cycle is considered an amphibolic pathway?

Accepted Answer

It is involved in both the oxidation of nutrients for energy and the provision of intermediates for biosynthesis.

Question 2

Where in a eukaryotic cell do most reactions of the citric acid cycle occur?

Accepted Answer

Mitochondrial matrix

Question 3

Which enzyme of the citric acid cycle is uniquely associated with the inner mitochondrial membrane rather than the mitochondrial matrix?

Accepted Answer

Succinate dehydrogenase

Question 4

What is the immediate fate of pyruvate produced by glycolysis under aerobic conditions?

Accepted Answer

It is converted to acetyl-CoA by oxidative decarboxylation.

Question 5

Which of the following equations correctly represents the overall carbon change during the conversion of pyruvate to acetyl-CoA?

Accepted Answer

$$	ext{Pyruvate (3C)} ightarrow 	ext{Acetyl-CoA (2C)} + 	ext{CO}_2$$

Question 6

Which of the following is NOT a major product of one turn of the citric acid cycle?

Accepted Answer

$$2 \ 	ext{ATP}$$

Question 7

Why is the citric acid cycle considered part of aerobic metabolism even though it does not directly consume $$	ext{O}_2$$?

Accepted Answer

Because the regeneration of $$	ext{NAD}^+$$ and $$	ext{FAD}$$ depends on the electron transport chain, which uses $$	ext{O}_2 as $$the final electron acceptor.

Question 8

If the conversion of pyruvate to acetyl-CoA is inhibited, what is the most immediate effect on the citric acid cycle?

Accepted Answer

Decreased entry of glucose-derived carbon into the cycle

Question 9

Which of the following best describes the fate of the two carbon atoms from acetyl-CoA during one turn of the citric acid cycle?

Accepted Answer

They enter the cycle and are eventually released as $$	ext{CO}_2$$, but not necessarily in the same turn.

Question 10

Which of the following reactions in the citric acid cycle involves FAD as the immediate electron acceptor?

Accepted Answer

Succinate to fumarate

Question 11

What is the energetic equivalence of the GTP produced in one turn of the citric acid cycle?

Accepted Answer

It is equivalent to 1 ATP molecule.

Question 12

Which of the following best summarizes the products generated from one molecule of glucose after two turns of the citric acid cycle?

Accepted Answer

$$6 \ 	ext{NADH}, \ 2 \ 	ext{FADH}_2, \ 2 \ 	ext{GTP}, \ 4 \ 	ext{CO}_2$$

Question 13

Which of the following statements about the role of NAD⁺ and FAD in the citric acid cycle is correct?

Accepted Answer

NAD⁺ and FAD are reduced to NADH and FADH₂, capturing electrons from oxidation reactions.

Question 14

Which of the following best describes the sequence of metabolic events from glucose to ATP production in aerobic metabolism?

Accepted Answer

Glucose → Glycolysis → Pyruvate → Acetyl-CoA → Citric acid cycle → NADH/FADH₂ → Electron transport chain → ATP

Question 15

Which of the following is a direct high-energy product of the citric acid cycle that can be used to generate ATP?

Accepted Answer

GTP

Question 16

Which of the following statements about the regeneration of oxaloacetate in the citric acid cycle is correct?

Accepted Answer

Oxaloacetate is regenerated at the end of each turn, allowing the cycle to continue.

The Central Role and Overall Pathway of the Citric Acid Cycle

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