Question 1

Which of the following best describes the main function of the citric acid cycle in cellular respiration?

Accepted Answer

To generate high-energy electron carriers (NADH and FADH2) for use in the electron transport system

Question 2

During the citric acid cycle, what is the fate of the carbons from the original acetyl group?

Accepted Answer

They are released as $$CO_2$$

Question 3

Which coenzyme is reduced to FADH2 during the citric acid cycle, and at which step does this occur?

Accepted Answer

FAD; during the conversion of succinate to fumarate

Question 4

What is the total net gain of ATP molecules from one molecule of glucose after all stages of aerobic cellular respiration are complete?

Accepted Answer

$$36$$

Question 5

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

Accepted Answer

Electron transport system and oxidative phosphorylation

Question 6

What is the role of oxygen in the electron transport system?

Accepted Answer

It accepts electrons and hydrogen ions to form water

Question 7

If a cell is deprived of oxygen, which of the following will occur?

Accepted Answer

Pyruvate will be converted to lactic acid

Question 8

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

Accepted Answer

Fats contain more carbon-hydrogen bonds, leading to more acetyl groups entering the citric acid cycle

Question 9

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

Accepted Answer

$$H_2O$$

Question 10

How does the energy from NADH and FADH2 contribute to ATP synthesis in the electron transport system?

Accepted Answer

By providing electrons that power proton pumps, creating a gradient used by ATP synthase

Question 11

Which of the following statements about protein catabolism is correct?

Accepted Answer

Amino acids are deaminated, and the remaining carbon backbone enters the citric acid cycle

Question 12

What is the main reason why lactic acid builds up in muscle tissue during intense exercise?

Accepted Answer

Oxygen is not available, so pyruvate is converted to lactic acid

Question 13

Which of the following best describes substrate-level phosphorylation?

Accepted Answer

ATP is produced directly by transferring a phosphate group to ADP from a high-energy substrate

Question 14

Which step in cellular respiration is responsible for the production of the most water molecules?

Accepted Answer

Electron transport system

Question 15

A patient is experiencing muscle cramps after sprinting. Which metabolic process is most likely responsible for this symptom?

Accepted Answer

Anaerobic glycolysis leading to lactic acid accumulation

Question 16

Which of the following equations 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 17

Which of the following is NOT a direct product of the citric acid cycle (for one glucose molecule)?

Accepted Answer

Lactic acid

Question 18

Why is the net gain of ATP from one glucose molecule during aerobic respiration 36 instead of 38?

Accepted Answer

Two ATP are used to transport NADH from the cytoplasm into the mitochondria

Question 19

Which of the following statements about the recycling of coenzymes in cellular respiration is correct?

Accepted Answer

NADH and FADH2 are oxidized in the electron transport system and recycled

Question 20

Which of the following best explains why the citric acid cycle is considered a cycle?

Accepted Answer

It regenerates oxaloacetate, which combines with acetyl CoA to begin the next turn

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

Study Guide - Practice Questions