Question 1

Which of the following inhibitors specifically blocks electron transport in Complex III by preventing the transfer of electrons between cytochrome b and coenzyme Q at the Q	extsubscript{o} site?

Accepted Answer

Antimycin A

Question 2

A patient is exposed to cyanide. Which of the following best describes the effect of cyanide on the electron transport chain?

Accepted Answer

It inhibits Complex IV by binding to the iron atom in cytochrome a	extsubscript{3}.

Question 3

Which of the following compounds acts as an uncoupler of oxidative phosphorylation, dissipating the proton gradient across the mitochondrial membrane?

Accepted Answer

Dinitrophenol (DNP)

Question 4

The P/O ratio is defined as the number of ATP molecules formed per 2 electrons transferred to oxygen. What is the P/O ratio for NADH?

Accepted Answer

$$2.5$$

Question 5

Which of the following best explains why oligomycin inhibits ATP synthesis?

Accepted Answer

It binds to ATP synthase and prevents protons from passing through the channel.

Question 6

A researcher adds rotenone to isolated mitochondria. Which of the following will be directly inhibited?

Accepted Answer

Transfer of electrons from NADH to ubiquinone (Q)

Question 7

Which of the following best describes the effect of an uncoupler such as DNP on mitochondrial function?

Accepted Answer

Electron transport continues but ATP synthesis decreases.

Question 8

Which of the following is a physiological uncoupler that enables brown adipose tissue to generate heat?

Accepted Answer

Uncoupling protein 1 (UCP1, thermogenin)

Question 9

Which of the following best describes the role of the ATP/ADP translocase in mitochondria?

Accepted Answer

It exchanges ATP from the matrix for ADP from the cytosol.

Question 10

Which of the following statements about the malate-aspartate shuttle is correct?

Accepted Answer

It transfers cytosolic NADH electrons into the mitochondria, yielding 2.5 ATP per NADH.

Question 11

Which of the following best explains why cyanide poisoning is rapidly fatal?

Accepted Answer

It blocks electron flow to oxygen, halting ATP synthesis.

Question 12

Which of the following is the correct equation for the complete oxidation of glucose?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} + 6\ \mathrm{O_2$} \rightarrow 6\ \mathrm{CO_2$} + 6\ \mathrm{H_2O} + 32\ \mathrm{ATP}$$

Question 13

Which of the following best describes the effect of oligomycin on the proton motive force?

Accepted Answer

It increases the proton gradient by blocking proton flow through ATP synthase.

Question 14

Which of the following best explains why the P/O ratio for FADH$$_2 is $$lower than for NADH?

Accepted Answer

FADH$$_2$$ donates electrons to Complex II, bypassing Complex I and resulting in fewer protons pumped.

Question 15

Which of the following best describes the function of the phosphate carrier protein in mitochondria?

Accepted Answer

It symports inorganic phosphate and a proton into the matrix.

Question 16

Which of the following is a direct effect of adding an uncoupler to actively respiring mitochondria?

Accepted Answer

Increased oxygen consumption

Question 17

Which of the following best explains why the ATP/ADP translocase is essential for oxidative phosphorylation?

Accepted Answer

It exchanges cytosolic ADP for mitochondrial ATP, enabling ATP export to the cytosol.

Question 18

Which of the following best describes the effect of carboxin on the electron transport chain?

Accepted Answer

It inhibits Complex II by blocking electron transfer from succinate to ubiquinone.

Question 19

Which of the following is the main reason why the glycerophosphate shuttle yields less ATP per cytosolic NADH than the malate-aspartate shuttle?

Accepted Answer

It transfers electrons to FAD in the mitochondria, yielding FADH$$_2$$ instead of NADH.

Inhibitors, Uncouplers, and Regulation of the Electron Transport Chain & ATP Synthesis

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