Question 1

Which of the following statements best describes the role of oxygen in oxidative phosphorylation?

Accepted Answer

Oxygen is the terminal electron acceptor, allowing electrons to flow through the electron transport chain and form water.

Question 2

Which complex of the electron transport chain receives electrons from FADH$_2$?

Accepted Answer

Complex II (Succinate dehydrogenase)

Question 3

What is the main consequence of inhibiting Complex IV (cytochrome c oxidase) in the electron transport chain?

Accepted Answer

Electron flow through the chain halts, leading to decreased ATP production and possible cell death.

Question 4

Which shuttle system is responsible for transferring cytosolic NADH into the mitochondria for oxidative phosphorylation?

Accepted Answer

Glycerol-3-phosphate shuttle

Question 5

Insulin inhibits which metabolic pathway that feeds electrons into the electron transport chain?

Accepted Answer

Beta-oxidation of fatty acids

Question 6

Which of the following correctly matches the electron carrier with its function in the electron transport chain?

Accepted Answer

Coenzyme Q (ubiquinone): Mobile lipid electron carrier between Complex I/II and Complex III

Question 7

A patient is exposed to cyanide, which inhibits Complex IV. What is the expected effect on cellular metabolism?

Accepted Answer

Accumulation of NADH and FADH$_2$ due to halted electron flow

Question 8

Which of the following best explains why 2,4-dinitrophenol (DNP) causes rapid heat production in cells?

Accepted Answer

DNP collapses the proton gradient, uncoupling electron transport from ATP synthesis and releasing energy as heat.

Question 9

How many ATP molecules are produced per NADH oxidized in the electron transport chain?

Accepted Answer

$\sim$2.5 ATP

Question 10

Which of the following is a direct result of the proton gradient established by the electron transport chain?

Accepted Answer

Synthesis of ATP from ADP and P$_i$ via ATP synthase

Question 11

During intense exercise, when oxygen supply is limited, which metabolic adaptation occurs to regenerate NAD$^+$?

Accepted Answer

Pyruvate is converted to lactate via lactate dehydrogenase.

Question 12

Which of the following toxins specifically inhibits ATP synthase?

Accepted Answer

Oligomycin

Question 13

Which of the following best describes the flow of electrons from NADH through the electron transport chain?

Accepted Answer

NADH $\rightarrow$ Complex I $\rightarrow$ CoQ $\rightarrow$ Complex III $\rightarrow$ Cyt c $\rightarrow$ Complex IV $\rightarrow$ O$_2$

Question 14

Which of the following is NOT a function of the electron transport chain?

Accepted Answer

Directly synthesizing ATP from ADP and P$_i$

Question 15

A mutation impairs the function of Coenzyme Q (ubiquinone). Which of the following is most likely to occur?

Accepted Answer

Electron flow from Complex I and II to Complex III is disrupted, reducing ATP synthesis.

Question 16

Which of the following best explains why inhibition of Complex I by rotenone leads to lactic acidosis?

Accepted Answer

Inhibition of Complex I increases glycolysis and lactate production due to impaired NAD$^+$ regeneration.

Question 17

Which of the following electron carriers is a small, soluble heme protein located in the intermembrane space?

Accepted Answer

Cytochrome c

Question 18

Which metabolic pathway produces both cholesterol and CoQ precursors, and may be affected by statin drugs?

Accepted Answer

Mevalonate pathway

Question 19

Which of the following is TRUE regarding the ATP yield from complete aerobic oxidation of one glucose molecule?

Accepted Answer

$30$-$32$ ATP are produced, depending on the shuttle system used for cytosolic NADH.

Oxidative Phosphorylation and the Electron Transport Chain: Biochemical Pathways and Mechanisms

Study Guide - Practice Questions