Question 1

Which of the following best describes the main function of the electron transport chain in mitochondria?

Accepted Answer

It pumps protons (H⁺) across the inner mitochondrial membrane to create a proton gradient.

Question 2

During aerobic respiration, what is the final electron acceptor in the electron transport chain?

Accepted Answer

O₂

Question 3

Which process is responsible for the majority of ATP production in eukaryotic cells?

Accepted Answer

Oxidative phosphorylation

Question 4

If the inner mitochondrial membrane becomes permeable to protons (H⁺), what is the most likely immediate effect on ATP synthesis?

Accepted Answer

ATP synthesis would decrease because the proton gradient would dissipate.

Question 5

Which of the following equations correctly represents the reaction catalyzed by ATP synthase?

Accepted Answer

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

Question 6

Brown adipose tissue (BAT) contains uncoupling protein 1 (UCP1). What is the physiological consequence of UCP1 activity?

Accepted Answer

Heat generation due to dissipation of the proton gradient.

Question 7

Which of the following statements about glycolysis is correct?

Accepted Answer

It occurs in the cytosol.

Question 8

What would happen to NADH oxidation and ATP synthesis if oxygen were suddenly removed from a respiring cell?

Accepted Answer

NADH oxidation and ATP synthesis by oxidative phosphorylation would both stop.

Question 9

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

Accepted Answer

It generates reduced electron carriers (NADH and FADH₂) that feed into the electron transport chain.

Question 10

A newborn mammal relies on brown adipose tissue for thermogenesis. What is the main advantage of this adaptation?

Accepted Answer

It allows the newborn to generate heat without shivering, maintaining body temperature.

Question 11

Which of the following is a direct result of electron flow through the electron transport chain?

Accepted Answer

Pumping of protons (H⁺) from the mitochondrial matrix to the intermembrane space.

Question 12

Why is the actual ATP yield per glucose molecule in eukaryotic cells not a fixed number?

Accepted Answer

Because electron shuttling, proton leakage, and other uses of the gradient can vary.

Question 13

Which of the following best describes substrate-level phosphorylation?

Accepted Answer

ATP is generated by the direct transfer of a phosphate group to ADP from a phosphorylated intermediate.

Question 14

If a poison blocks the function of ATP synthase, which of the following would occur?

Accepted Answer

Electron transport would continue, but ATP production would stop.

Question 15

Which equation represents the reduction of oxygen at the end of the electron transport chain?

Accepted Answer

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

Question 16

A tissue with high mitochondrial density but low ATP demand at rest is most likely to:

Accepted Answer

Adjust its ATP production to match its metabolic demand.

Question 17

Which of the following best explains why some energy from glucose metabolism is released as heat?

Accepted Answer

Energy transformations are never perfectly efficient, and some energy is lost as heat.

Question 18

Which of the following would most likely occur if cyanide is introduced to a cell?

Accepted Answer

Electron transport would be blocked, preventing ATP synthesis by oxidative phosphorylation.

Question 19

Which of the following is a correct sequence of energy conversion during aerobic respiration?

Accepted Answer

Chemical energy in food → high-energy electrons in NADH/FADH₂ → proton-motive force → ATP

Question 20

Which of the following best explains why ATP production is necessary but not sufficient to explain organismal growth?

Accepted Answer

Growth also depends on the allocation of energy and nutrients among tissues, not just ATP availability.

Cellular Respiration: ATP Generation, Electron Transport, and Metabolic Regulation

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