Question 1

Which of the following best describes the primary function of the electron transport chain (ETC) in mitochondria?

Accepted Answer

To transfer electrons from NADH and FADH2 to oxygen, creating a proton gradient across the inner mitochondrial membrane.

Question 2

What is the ultimate electron acceptor in the mitochondrial electron transport chain during aerobic respiration?

Accepted Answer

Oxygen (O2)

Question 3

Which of the following respiratory complexes does NOT contribute to proton pumping across the inner mitochondrial membrane?

Accepted Answer

Complex II

Question 4

If cyanide is introduced to a cell, which process is directly inhibited?

Accepted Answer

The transfer of electrons from cytochrome c oxidase (Complex IV) to oxygen

Question 5

Which molecule acts as a mobile electron carrier between Complex III and Complex IV in the ETC?

Accepted Answer

Cytochrome c

Question 6

What is the main consequence of using an uncoupler such as 2,4-dinitrophenol (DNP) on mitochondrial function?

Accepted Answer

Decreased ATP production and increased oxygen consumption

Question 7

Which equation correctly represents the maximum theoretical ATP yield from the complete aerobic oxidation of one molecule of glucose?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} + 6\mathrm{O_2$} + 38\mathrm{ADP} + 38\mathrm{P_i} \rightarrow 6\mathrm{CO_2$} + 6\mathrm{H_2O} + 38\mathrm{ATP}$$

Question 8

Which of the following best explains why the actual ATP yield per glucose is often less than the theoretical maximum in eukaryotic cells?

Accepted Answer

Some protons leak across the inner mitochondrial membrane and are used for other transport processes.

Question 9

Which component of the ATP synthase complex is responsible for the actual synthesis of ATP from ADP and Pi?

Accepted Answer

F1 subunit

Question 10

A patient is exposed to rotenone, a poison that inhibits Complex I of the ETC. What is the most immediate effect on cellular respiration?

Accepted Answer

Electron flow from NADH to the ETC is blocked, reducing ATP synthesis.

Question 11

Which of the following statements about the chemiosmotic model is correct?

Accepted Answer

The proton gradient across the inner mitochondrial membrane provides the energy for ATP synthesis.

Question 12

Which of the following best describes the role of coenzyme Q (ubiquinone) in the ETC?

Accepted Answer

It shuttles electrons between Complex I/II and Complex III.

Question 13

If a mutation caused the inner mitochondrial membrane to become highly permeable to protons, what would be the most likely outcome?

Accepted Answer

ATP synthesis would decrease due to dissipation of the proton gradient.

Question 14

Which of the following is a direct result of the inhibition of ATP synthase by oligomycin?

Accepted Answer

Proton flow through ATP synthase is blocked, halting ATP production.

Question 15

Which of the following best explains why oxygen is essential for the operation of the ETC?

Accepted Answer

Oxygen acts as the final electron acceptor, allowing the chain to continue functioning.

Question 16

Which of the following scenarios would most likely lead to increased heat production in a cell?

Accepted Answer

Addition of an uncoupler such as FCCP

Question 17

Which of the following best describes the relationship between electron transport and ATP synthesis?

Accepted Answer

ATP synthesis is dependent on electron transport, but electron transport can occur without ATP synthesis.

Question 18

Which of the following is a function of the respirasome supercomplexes in the inner mitochondrial membrane?

Accepted Answer

They minimize diffusion distances for substrates and intermediates, increasing efficiency.

Question 19

Which of the following factors does NOT directly regulate the activity of the electron transport chain?

Accepted Answer

Concentration of glucose in the cytosol

The Electron Transport Chain and ATP Synthesis in Aerobic Respiration

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