Question 1

Which of the following statements best describes the main purpose of the citric acid cycle in aerobic respiration?

Accepted Answer

To fully oxidize carbon from acetyl-CoA to CO$$_2$$ and store released energy in NADH and FADH$$_2.$$

Question 2

During aerobic respiration, which compartment of the mitochondrion is the site of the citric acid cycle?

Accepted Answer

Matrix

Question 3

Which enzyme catalyzes the conversion of pyruvate to acetyl-CoA, and what are the products of this reaction?

Accepted Answer

Pyruvate dehydrogenase; acetyl-CoA, CO$$_2$$, and NADH

Question 4

Which of the following best explains why NADH yields more ATP than FADH$$_2$$ during oxidative phosphorylation?

Accepted Answer

NADH donates electrons at Complex I, resulting in more protons pumped across the membrane.

Question 5

A patient is exposed to cyanide, which inhibits Complex IV of the electron transport chain. What is the most immediate cellular consequence?

Accepted Answer

Electron flow through the ETC will stop, halting proton gradient formation.

Question 6

Which of the following is NOT a function of the mitochondrial inner membrane?

Accepted Answer

Contains porins for free passage of small molecules

Question 7

In the citric acid cycle, which step is directly responsible for substrate-level phosphorylation?

Accepted Answer

Succinyl-CoA to succinate

Question 8

Which of the following best describes the role of cristae in mitochondria?

Accepted Answer

They increase the surface area for electron transport and ATP production.

Question 9

Which of the following is a correct summary of the total products generated from one glucose molecule after pyruvate oxidation and the citric acid cycle?

Accepted Answer

8 NADH, 2 FADH$$_2$$, 2 ATP, 6 CO$$_2$$

Question 10

Which of the following statements about the amphibolic nature of the citric acid cycle is TRUE?

Accepted Answer

It is involved in both catabolism and anabolism, breaking down fuels and providing precursors for biosynthesis.

Question 11

Which mitochondrial compartment accumulates protons during electron transport, creating the gradient used for ATP synthesis?

Accepted Answer

Intermembrane space

Question 12

Which of the following is a direct consequence of inhibiting the pyruvate symporter in the inner mitochondrial membrane?

Accepted Answer

Pyruvate cannot enter the matrix, preventing acetyl-CoA formation.

Question 13

Which of the following best describes the regulation of the citric acid cycle when cellular energy is high?

Accepted Answer

High ATP and NADH inhibit key dehydrogenases and PDH.

Question 14

Which electron carrier in the ETC is a non-protein molecule that shuttles electrons and protons within the inner membrane?

Accepted Answer

Coenzyme Q (ubiquinone)

Question 15

Which step in the citric acid cycle produces FADH$$_2$$ and is catalyzed by an enzyme that is also part of the electron transport chain?

Accepted Answer

Succinate to fumarate, catalyzed by succinate dehydrogenase

Question 16

Which of the following equations correctly represents the overall reaction for ATP synthesis by ATP synthase?

Accepted Answer

$$\mathrm{ADP} + \mathrm{P_i} \rightarrow \mathrm{ATP}$$

Question 17

Which of the following best explains why the glyoxylate cycle is important in plants but not in most animals?

Accepted Answer

It allows plants to convert fat into glucose during seed germination by bypassing CO$$_2-$$releasing steps.

Question 18

Which of the following is a correct description of the flow of electrons in the electron transport chain?

Accepted Answer

Electrons move from NADH/FADH$$_2 to O$_2$$, releasing energy in small steps.

Question 19

Which of the following is a plausible outcome if a mutation prevents the removal of the transit sequence from a mitochondrial protein after import?

Accepted Answer

The protein may fail to fold properly and remain nonfunctional in the matrix.

Aerobic Respiration and the Mitochondrion: Citric Acid Cycle, Electron Transport Chain, and ATP Synthesis

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