Question 1

Which of the following best describes the fate of pyruvate during anaerobic respiration in human muscle cells?

Accepted Answer

Pyruvate is converted into lactic acid in the cytoplasm.

Question 2

During the citric acid cycle, what is the primary role of NAD+?

Accepted Answer

To pick up hydrogen ions and electrons, becoming NADH.

Question 3

How many molecules of ATP are produced by substrate-level phosphorylation during the citric acid cycle for each molecule of glucose?

Accepted Answer

$$2$$

Question 4

Which of the following is a waste product of the electron transport system?

Accepted Answer

H$$_2O$$

Question 5

What is the net gain of ATP molecules from the complete aerobic catabolism of one molecule of glucose, accounting for the cost of shuttling NADH into the mitochondria?

Accepted Answer

$$36$$

Question 6

Which process is responsible for the majority of ATP production during cellular respiration?

Accepted Answer

Electron transport system (oxidative phosphorylation)

Question 7

What happens to the electrons carried by NADH and FADH$$_2$$ during the electron transport system?

Accepted Answer

They are passed along carrier proteins, powering the active transport of H$$^+$$ ions.

Question 8

Which of the following statements about fat metabolism is correct?

Accepted Answer

Fatty acids are converted into acetyl groups that enter the citric acid cycle.

Question 9

What is the role of ATP synthase in the mitochondria?

Accepted Answer

It catalyzes the synthesis of ATP as H$$^+$$ ions diffuse through it.

Question 10

Which of the following best explains why the citric acid cycle must occur twice for each glucose molecule?

Accepted Answer

Each glucose produces two pyruvate molecules, which are converted to two acetyl CoA molecules.

Question 11

Which of the following is a direct result of the removal of the amine group from amino acids during protein catabolism?

Accepted Answer

Production of urea, which is excreted in urine

Question 12

Which equation correctly represents the formation of water at the end of the electron transport system?

Accepted Answer

$$\frac{1}{2} O_2$ + 2H^+ + 2e^- \rightarrow H_2O$$

Question 13

Which of the following is NOT a product of the citric acid cycle (for both acetyl groups from one glucose)?

Accepted Answer

6 H$$_2O$$

Question 14

What is the main reason why energy is released slowly during cellular respiration?

Accepted Answer

To allow for efficient capture and use of energy.

Question 15

Which of the following best describes oxidative phosphorylation?

Accepted Answer

ATP production using energy from the movement of H$$^+$$ ions through ATP synthase.

Question 16

If a poison blocks the function of ATP synthase, which of the following would be the most immediate effect?

Accepted Answer

H$$^+$$ ions would accumulate in the intermembrane space.

Question 17

Which of the following statements about protein catabolism is correct?

Accepted Answer

The carbon backbone of amino acids enters the citric acid cycle at various points.

Question 18

Which of the following is the correct sequence of events for the complete aerobic breakdown of glucose?

Accepted Answer

Glycolysis → Preparatory Step → Citric Acid Cycle → Electron Transport System

Question 19

Which of the following best explains why fats yield more ATP than glycogen when metabolized?

Accepted Answer

Fats contain more carbon-hydrogen bonds, providing more acetyl groups for the citric acid cycle.

Question 20

Which of the following is a direct consequence of the active transport of H$$^+$$ ions to the outer mitochondrial membrane during the electron transport system?

Accepted Answer

A proton gradient is established, which drives ATP synthesis.

Cellular Respiration: Citric Acid Cycle, Electron Transport System, and Alternative Energy Sources

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