Q: What is the net reaction for the conversion of 2 pyruvate molecules through the Citric Acid Cycle (including the link reaction)?

$$2 \text{ pyruvate} \rightarrow 2 \text{ acetyl-CoA} + 4 CO_2$ + 2 $$FADH_2$$ + 6 NADH + 2 ATP$$

Question 1

Which of the following is the primary purpose of the Citric Acid Cycle (Krebs Cycle) in cellular respiration?

Accepted Answer

To generate electron carriers (NADH and FADH$$_2) $$for the electron transport chain

Question 2

What is the initial substrate that enters the Citric Acid Cycle after glycolysis?

Accepted Answer

Acetyl-CoA

Question 3

Which of the following best describes the fate of carbon atoms from glucose during the Citric Acid Cycle?

Accepted Answer

They are released as $$CO_2$$

Question 4

How many NADH molecules are produced from one turn of the Citric Acid Cycle?

Accepted Answer

3

Question 5

Which enzyme catalyzes the conversion of citrate to isocitrate in the Citric Acid Cycle?

Accepted Answer

Aconitase

Question 6

If a cell is deprived of oxygen, which process directly stops first?

Accepted Answer

Electron Transport Chain

Question 7

Which of the following is NOT a product of the Citric Acid Cycle per acetyl-CoA molecule?

Accepted Answer

Glucose

Question 8

What is the net reaction for the conversion of 2 pyruvate molecules through the Citric Acid Cycle (including the link reaction)?

Accepted Answer

$$2 	ext{ pyruvate} ightarrow 2 	ext{ acetyl-CoA} + 4 CO_2$ + 2 $$FADH_2$$ + 6 NADH + 2 ATP$$

Question 9

Which molecule acts as the final electron acceptor in the electron transport chain, which is fueled by NADH and FADH$$_2$$ from the Citric Acid Cycle?

Accepted Answer

Oxygen ($$O_2)$$

Question 10

A mutation in the gene encoding succinate dehydrogenase would most directly affect which step of the Citric Acid Cycle?

Accepted Answer

Conversion of succinate to fumarate

Question 11

Which of the following best explains why all organisms perform the Citric Acid Cycle or a similar pathway?

Accepted Answer

It is essential for generating electron carriers for oxidative phosphorylation

Question 12

During the Citric Acid Cycle, which step directly produces ATP (or GTP) via substrate-level phosphorylation?

Accepted Answer

Conversion of succinyl-CoA to succinate

Question 13

Which of the following statements about the Citric Acid Cycle is FALSE?

Accepted Answer

It directly consumes oxygen

Question 14

If a toxin inhibits the enzyme that converts pyruvate to acetyl-CoA, what would be the immediate effect on cellular respiration?

Accepted Answer

The Citric Acid Cycle would not proceed

Question 15

Which of the following is a correct summary of the products generated from one molecule of acetyl-CoA in the Citric Acid Cycle?

Accepted Answer

2 NADH, 1 FADH$$_2$$, 1 ATP (or GTP), 2 CO$$_2$$

Question 16

Which of the following best describes the role of NAD$$^+ in $$the Citric Acid Cycle?

Accepted Answer

It serves as an electron carrier, accepting electrons during oxidation reactions

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