Question 1

Which of the following best describes the chemiosmotic theory as it applies to oxidative phosphorylation?

Accepted Answer

Transmembrane differences in proton concentration store energy used to drive ATP synthesis.

Question 2

Which of the following statements about NADH and FADH$$_2 is $$CORRECT?

Accepted Answer

NADH is water soluble and cannot cross the inner mitochondrial membrane.

Question 3

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

Accepted Answer

Cytochrome c: Transfers electrons from Complex III to Complex IV.

Question 4

Which of the following best explains why Complex II does NOT contribute to the proton gradient across the inner mitochondrial membrane?

Accepted Answer

It lacks the structural components necessary to pump protons.

Question 5

A patient is exposed to arsenic, which inhibits the pyruvate dehydrogenase complex. What is the most immediate metabolic consequence?

Accepted Answer

Decreased formation of acetyl-CoA from pyruvate, reducing TCA cycle activity.

Question 6

Which of the following equations correctly represents the free energy change ($$\Delta G) $$for proton movement across the mitochondrial membrane?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{C_2}{C_1} \right) + ZF\Delta \Psi$$

Question 7

Which of the following statements about the Q cycle in Complex III is TRUE?

Accepted Answer

It couples the transfer of electrons from ubiquinol to cytochrome c with the translocation of protons.

Question 8

Which of the following best describes the role of iron-sulfur proteins in the electron transport chain?

Accepted Answer

They participate in one-electron transfers and their reduction potential depends on the protein environment.

Question 9

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

Accepted Answer

Pumping of four protons from the matrix to the intermembrane space.

Question 10

Which of the following best explains why NADH produced in the cytosol cannot directly contribute electrons to the mitochondrial electron transport chain?

Accepted Answer

The inner mitochondrial membrane is impermeable to NADH.

Question 11

Which of the following correctly describes the fate of electrons from FADH$$_2$$ generated during fatty acid oxidation?

Accepted Answer

They are transferred to ubiquinone via ETF:Q oxidoreductase.

Question 12

Which of the following is TRUE regarding the energy conservation in oxidative phosphorylation?

Accepted Answer

The energy released from electron transfer is used to create a proton gradient across the inner mitochondrial membrane.

Question 13

Which of the following best describes the function of cytochrome c in the electron transport chain?

Accepted Answer

It is a soluble protein that transfers electrons from Complex III to Complex IV.

Question 14

A mutation causes Complex IV to lose its copper centers. Which process would be most directly affected?

Accepted Answer

Reduction of O$$_2 to H$_2O.$$

Question 15

Which of the following is a correct net equation for the reaction catalyzed by Complex IV?

Accepted Answer

$$2	ext{cyt c (red)} + 4	ext{H}^+ + \frac{1}{2}O_2 ightarrow 2	ext{cyt c (ox)} + 2	ext{H}_2O$$

Question 16

Which of the following statements about the mitochondrial inner membrane is CORRECT?

Accepted Answer

It contains the components of the respiratory chain and ATP synthase.

Question 17

Which of the following best explains why the energy from the proton gradient is sufficient to drive ATP synthesis?

Accepted Answer

The energy available from the proton gradient (about 220 kJ/mol) is much greater than the energy required to synthesize ATP (about 50 kJ/mol).

Oxidative Phosphorylation and the Electron Transport Chain

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