Q: Which equation correctly represents the standard free energy change for a redox reaction?

$$ \Delta G^\circ' = -nF (E^\circ_{\text{acceptor}} - E^\circ_{\text{donor}}) $$

Q: If the standard reduction potential difference ($$ \Delta E^\circ' $$) for the transfer of electrons from NADH to O$_2$ is 1.14 V, how much standard free energy change ($$ \Delta G^\circ' $$) is released per mole of electrons transferred? (Use $F = 96,485$ J mol$^{-1}$ V$^{-1}$, $n=2$)

$$ \Delta G^\circ' = -2 \times 96,485 \times 1.14 = -220,382 \text{ J/mol} $$

Question 1

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

Accepted Answer

It transfers electrons from reduced electron carriers to oxygen, generating a proton gradient used for ATP synthesis.

Question 2

Which equation correctly represents the standard free energy change for a redox reaction?

Accepted Answer

$$ \Delta G^\circ' = -nF (E^\circ_{	ext{acceptor}} - E^\circ_{	ext{donor}}) $$

Question 3

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

Accepted Answer

Complex II (Succinate-Coenzyme Q Reductase)

Question 4

During the Q cycle in Complex III, how many protons are pumped into the intermembrane space per pair of electrons transferred from CoQH$_2$ to cytochrome c?

Accepted Answer

4

Question 5

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

Accepted Answer

FADH$_2$ donates electrons to Complex II, which does not pump protons, resulting in fewer protons being translocated per electron pair.

Question 6

A patient is exposed to dinitrophenol (DNP), an uncoupling agent. Which of the following outcomes would you expect in their mitochondria?

Accepted Answer

Electron transport continues, but ATP synthesis is inhibited due to dissipation of the proton gradient.

Question 7

Which of the following is the correct net equation for the oxidation of glucose during aerobic respiration?

Accepted Answer

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

Question 8

Which of the following statements about iron-sulfur clusters in the electron transport chain is TRUE?

Accepted Answer

They consist of nonheme iron complexed with thiol sulfurs of cysteine residues.

Question 9

If the standard reduction potential difference ($$ \Delta E^\circ' $$) for the transfer of electrons from NADH to O$_2$ is 1.14 V, how much standard free energy change ($$ \Delta G^\circ' $$) is released per mole of electrons transferred? (Use $F = 96,485$ J mol$^{-1}$ V$^{-1}$, $n=2$)

Accepted Answer

$$ \Delta G^\circ' = -2 	imes 96,485 	imes 1.14 = -220,382 	ext{ J/mol} $$

Question 10

Which of the following best describes the role of ATP synthase (Complex V) in oxidative phosphorylation?

Accepted Answer

It uses the energy of the proton gradient to synthesize ATP from ADP and inorganic phosphate.

Question 11

Which of the following is a correct statement about the chemiosmotic coupling model?

Accepted Answer

A proton gradient across the inner mitochondrial membrane is used to drive ATP synthesis.

Question 12

Which of the following electron carriers is a lipid-soluble molecule that shuttles electrons between Complexes I/II and III?

Accepted Answer

Coenzyme Q (ubiquinone)

Question 13

A mutation causes Complex IV (cytochrome c oxidase) to lose its ability to bind oxygen. What is the most immediate consequence for the cell?

Accepted Answer

Electron flow through the respiratory chain will stop, halting ATP synthesis by oxidative phosphorylation.

Question 14

Which of the following best explains why the total ATP yield per mole of glucose is not always an integer?

Accepted Answer

The oxidation of NADH and FADH$_2$ is not directly coupled to ATP synthesis, and the P/O ratios are averages.

Question 15

Which of the following is TRUE regarding the experimental evidence for chemiosmotic coupling?

Accepted Answer

Uncoupling agents like DNP allow electron transport to occur without ATP synthesis.

Question 16

How many ATP molecules are produced from the complete oxidation of one molecule of glucose, assuming P/O ratios of 2.5 for NADH and 1.5 for FADH$_2$?

Accepted Answer

32

Question 17

Which of the following statements about cytochromes is correct?

Accepted Answer

They contain heme groups and are classified based on their absorption spectra.

Question 18

Which of the following best describes the path of electrons from succinate to oxygen in the mitochondrial respiratory chain?

Accepted Answer

Succinate → Complex II → Coenzyme Q → Complex III → Cytochrome c → Complex IV → O$_2$

Electron Transport, Oxidative Phosphorylation, and Oxygen Metabolism: Chapter 14 Study Notes

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