Question 1

Complex IV of the electron transport chain oxidizes ____, reduces ____, and ____ protons in the process.

Accepted Answer

D

Question 2

Which complex of the electron transport chain does NOT contain an iron-sulfur cluster?

Accepted Answer

Complex IV, also known as cytochrome c oxidase, does not contain an iron-sulfur cluster. It primarily contains copper centers and heme groups that are involved in the transfer of electrons to oxygen, the final electron acceptor.

Question 3

The final reduced species in the electron transport chain is

Accepted Answer

B

Question 4

Complex I of the electron transport chain oxidizes ____, reduces ____, and ____ protons in the process.

Accepted Answer

Complex I of the electron transport chain oxidizes NADH, reduces coenzyme Q, and pumps protons in the process.

Question 5

Which of the following is not true?

Accepted Answer

The synthesis of ATP is not directly linked to the oxidation of NADH. Instead, the oxidation of NADH and FADH2 indirectly creates a proton gradient that drives ATP synthesis.

Question 6

The pH of the mitochondrial matrix is ____ the pH of the intermembrane space.

Accepted Answer

The pH of the mitochondrial matrix is higher than the pH of the intermembrane space. This is because protons (H+) are actively pumped from the matrix into the intermembrane space, creating a proton gradient used for ATP synthesis.

Question 7

Complex II of the electron transport chain oxidizes ____, reduces ____, and ____ protons in the process.

Accepted Answer

Complex II oxidizes FADH2 to FAD, reduces coenzyme Q (ubiquinone) to ubiquinol, and does not pump protons across the mitochondrial membrane.

Question 8

The ultimate electron acceptor in the electron transport chain is

Accepted Answer

Oxygen is the final electron acceptor in the electron transport chain, which is essential for the production of ATP through oxidative phosphorylation.

Question 9

Which of the following statements concerning E° for an electron-transfer reaction is false?

Accepted Answer

E° is measured by comparison with a standard hydrogen electrode, not by comparison with the partial pressure of oxygen in the bloodstream or any other gas.

Question 10

To calculate the ΔG of a redox reaction, you need:

Accepted Answer

To calculate the ΔG of a redox reaction, you need the reduction potential (E°) of the half reactions to calculate the cell potential (E), which is used to calculate the Gibbs free energy change (ΔG) using the equation ΔG = -nFE, where n is the number of electrons involved in the transfer and F is the Faraday constant. Therefore, all of the given choices are needed to calculate ΔG.

Question 11

Which of the following is an advantage of using multiple steps in electron transport?

Accepted Answer

By using small steps in electron transport, more energy can be captured and used to synthesize ATP. This is because the small steps allow for greater efficiency in the transfer of energy from the electrons to ATP. Option A is incorrect, as a higher net −ΔG would actually make the process less efficient. Option B is incorrect as generating heat is not an advantage in itself. Option D is incorrect as heat generation and ATP synthesis are competing processes that cannot both be maximized at the same time. Option E contains all of the statements, but not all of them are advantages.

Question 12

The Q cycle refers to flow of electrons from

Accepted Answer

The Q cycle refers to the flow of electrons from coenzyme Q to cytochrome c via Complex III. This process involves the transfer of two electrons from the reduced coenzyme Q (ubiquinol) to a molecule of cytochrome c, leading to the generation of a proton gradient across the mitochondrial inner membrane.

Question 13

Which of the following is not a part of the electron transport chain?

Accepted Answer

Coenzyme A is not a part of the electron transport chain. It is involved in other metabolic pathways such as the Krebs cycle. The rest of the options, NADH, FADH2, and coenzyme Q, are all components of the electron transport chain.

Question 14

The reference reaction for determining reduction potentials (E° = 0) is the reduction of

Accepted Answer

The answer of The reference reaction for determining reduction potentials...

Question 15

Which of the following components of the electron transport chain can only participate in one-electron transfers?

Accepted Answer

Cytochrome C is the only component of the electron transport chain that can only participate in one-electron transfers. The other components, NAD, FAD, and coenzyme Q, can participate in two-electron transfers.

Question 16

Reduction potentials (E°) are measured by reading a voltmeter, which measures the electron flow between two reaction chambers.

Accepted Answer

Reduction potentials are indeed measured by reading a voltmeter, which measures the electron flow between two reaction chambers.

Question 17

How many electrons are required for the complete reduction of one molecule of oxygen gas?

Accepted Answer

The complete reduction of one molecule of oxygen gas (O2) to water (H2O) requires four electrons, according to the equation: O2 + 4e- + 4H+ → 2H2O.

Question 18

Complex III of the electron transport chain oxidizes ____, reduces ____, and ____ protons in the process.

Accepted Answer

Complex III of the electron transport chain oxidizes coenzyme Q (ubiquinone), reduces cytochrome c, and pumps protons across the mitochondrial membrane, contributing to the proton gradient used for ATP synthesis.

Question 19

When mitochondria are actively carrying out aerobic respiration

Accepted Answer

During aerobic respiration, protons (H+) are pumped from the matrix into the intermembrane space, creating a proton gradient. This results in a higher concentration of H+ in the intermembrane space, making it more acidic (lower pH) compared to the matrix, which becomes more alkaline (higher pH).

Question 20

Which of the following terms describes ATP synthesis in mitochondria?

Accepted Answer

ATP synthesis in mitochondria occurs through oxidative phosphorylation, which involves the transfer of electrons through the electron transport chain and the generation of a proton gradient across the inner mitochondrial membrane. This proton gradient is then used to drive the synthesis of ATP by the enzyme ATP synthase. Substrate-level phosphorylation occurs during glycolysis and the citric acid cycle, but not in mitochondrial ATP synthesis. Photophosphorylation is the process by which ATP is synthesized in photosynthetic organisms, and does not occur in mitochondria. Therefore, B (oxidative phosphorylation) is the best choice.

Quiz 20: Electron Transport and Oxidative Phosphorylation

Complex IV of the electron transport chain oxidizes , reduces , and protons in the process.