Deck 15: Electron Transport, Oxidative Phosphorylation, and Oxygen Metabolism

Question 1

Which of the following describes a correct and complete electron transfer pathway?

A)NADH $\rarr$ complex I $\rarr$ CoQ $\rarr$ complex III $\rarr$ cyt c $\rarr$ complex IV
B)NADH $\rarr$ complex I $\rarr$ complex II $\rarr$ CoQ $\rarr$ complex III $\rarr$ cyt c $\rarr$ complex IV
C)NADH $\rarr$ complex I $\rarr$ cyt c $\rarr$ complex III $\rarr$ CoQ $\rarr$ complex IV
D)FADH₂ $\rarr$ CoQ $\rarr$ complex II $\rarr$ complex III $\rarr$ cyt c $\rarr$ complex IV
E)FADH₂ $\rarr$ complex II $\rarr$ cyt c $\rarr$ complex III $\rarr$ CoQ $\rarr$ complex IV

Answer 1

NADH $\rarr$ complex I $\rarr$ CoQ $\rarr$ complex III $\rarr$ cyt c $\rarr$ complex IV

Question 2

What is the approximate P/O ratio if the source of electrons for the electron transport chain is FADH₂?

A)1
B)1.5
C)2
D)2.5
E)3

Answer 2

B

Question 3

The presence of 10 copies of the c subunit of the F₀ complex of yeast ATP synthase allows for the synthesis of 1 ATP for every ______ proton(s)that are translocated across the inner mitochondrial membrane.

A)10
B)4
C)3.3
D)2.5
E)1

Answer 3

C

Question 4

__________ increases oxygen consumption while decreasing ATP synthesis, but ____________ decreases both oxygen consumption and ATP synthesis.

A)rotenone; valinomycin
B)azide; 2,4-dinitrophenol
C)antimycin A; nigericin
D)2,4-dinitrophenol; oligomycin
E)cyanide; valinomycin

Question 5

In addition to iron, what metal is found in certain cytochromes?

A)manganese
B)copper
C)chromium
D)cobalt
E)zinc

Question 6

The inhibition by an unknown inhibitor of electron transport was found to be removed by a large concentration of phenazine methosulfate. Since phenazine methosulfate is known to accept electrons from cytochrome b of complex III, which of the following is most similar to the unknown inhibitor?

A)amytal
B)antimycin A
C)carbon monoxide
D)cyanide
E)rotenone

Question 7

Which of the following acts as an uncoupler of the mitochondrial proton gradient due to its action as an ionophore?

A)valinomycin
B)nigericin
C)trifluorocarbonylcyanide phenylhydrazone
D)2,4-dinitrophenol
E)cyanide

Question 8

Based on the following information, what is the $\Delta$ G ^$\circ$ $\alpha$ for the oxidation of malate by NAD⁺? NAD⁺ + H⁺ + 2e^-
NADH E ^$\circ$ ' = -0.32 V
Oxaloacetate + 2H⁺ + 2e^-
malate E ^$\circ$ ' = -0.17 V

A)-29 kJ/mol
B)29 kJ/mol
C)-95 kJ/mol
D)95 kJ/mol
E)none of the above

Question 9

Within the electron transport chain, complex _____ represents the entry point for electrons from NADH while complex _____ represents the entry point for electrons from FADH₂.

A)I; III
B)II; III
C)I; II
D)II; I
E)IV; III

Question 10

In the malate/aspartate shuttle, glutamate is converted to _________ in the mitochondria while aspartate is converted to ___________ in the cytosol.

A)oxaloacetate; malate
B) $\alpha$ -ketoglutarate; oxaloacetate
C)oxaloacetate; glutamate
D)aspartate; $\alpha$ -ketoglutarate
E)malate; oxaloacetate

Question 11

What is the approximate free energy for transporting a mole of protons from the matrix to the intermembrane space under normal conditions within the mitochondria?

A)+220 kJ/mol
B)+21 kJ/mol
C)-21 kJ/mol
D)-220 kJ/mol
E)none of the above

Question 12

Which of the following uses the energy of the proton gradient to drive transport of its substrates?

A)ADP/ATP carrier
B)phosphate translocase in symport mode
C)phosphate translocase in antiport mode
D)pyruvate transport system
E)all of the above

Question 13

If the following two reactions were coupled, what would be the oxidizing agent for the spontaneous reaction? NAD⁺ + H⁺ + 2e^-
NADH E ^$\circ$ ' = -0.32 V
Acetaldehyde + 2H⁺ + 2e^-
ethanol E ^$\circ$ ' = -0.20 V

A)NAD⁺
B)acetaldehyde
C)NADH
D)ethanol
E)H⁺

Question 14

Which amino acid is complexed to iron-sulfur clusters to enable them to associate with proteins?

A)methionine
B)serine
C)lysine
D)tyrosine
E)cysteine

Question 15

The oxidized form of coenzyme Q is considered a _______ while the reduced form is considered a _______.

A)semiquinone; quinone
B)quinone; semiquinone
C)quinone; hydroquinone
D)hydroquinone; quinone
E)semiquinone; hydroquinone

Question 16

Which of the following steps in the catalytic cycle of the F₁ component is the most energetically unfavorable?

A)binding of ADP
B)binding of P_i
C)formation of ATP from ADP and P_i
D)release of ATP
E)all of the above are equally energetically unfavorable

Question 17

Which of the following correctly describes what happens in the first stage of the Q cycle, considering that one cytochrome c is reduced in the process?

A)one QH₂ is oxidized to QH $\bullet$ while another Q $\bullet$ is reduced to QH₂
B)one QH₂ is reduced to QH $\bullet$ while another QH $\bullet$ is oxidized to Q
C)one QH₂ is oxidized to QH $\bullet$
D)one QH₂ is oxidized to Q while another Q is reduced to QH $\bullet$
E)none of the above

Question 18

Which of the following pathways takes place primarily within the inner mitochondrial membrane?

A)fatty acid $\beta$ -oxidation
B)electron transport
C)glycolysis
D)citric acid cycle
E)pentose phosphate pathway

Question 19

Rotation of the ____ subunit causes the _____ subunit to change from tight conformation where ATP is produced to open conformation where ATP is released.

A) $\gamma$ ; $\alpha$
B) $\gamma$ ; $\beta$$\gamma$
C) $\delta$ ; $\alpha$
D) $\delta$ ; $\beta$
E) $\varepsilon$ ; $\beta$

Question 20

Which of the following correctly indicates the number of protons pumped into the intermembrane space at each complex of electron transport for each FADH₂ that is oxidized by the electron transport pathway?

A)II: 2 III: 4 IV: 2
B)II: 0 III: 2 IV: 4
C)II: 2 III: 2 IV: 2
D)II: 0 III: 4 IV: 2
E)II: 0 III: 2 IV: 2

Question 21

A(n)_______ incorporates oxygen from O₂ into its products while a(n)_______ uses another oxidizing agent to accomplish the oxidation of its substrate.

A)oxidase; dioxygenase
B)dehydrogenase; oxygenase
C)oxygenase; oxidase
D)dehydrogenase; oxidase
E)dioxygenase; oxygenase

Question 22

Using the structure of coenzyme Q, show one reaction to produce the semiquinone and the subsequent reaction to produce the hydroquinone forms of the molecule. (R represents the isoprenoid tail).

Question 23

Which of the reactive oxygen species is thought to damage lipid membranes?

A)semiquinone radical
B)superoxide
C)nitric oxide
D)hydrogen peroxide
E)hydroxyl radical

Question 24

Use the following half reactions to determine the reaction found in the pyruvate dehydrogenase complex. Calculate the $\Delta$ G ^$\circ$ for the reaction.
lipoate + 2H⁺ + 2e^-
dihydrolipoate E ^$\circ$ ' = -0.29 V
FAD + 2H⁺ + 2e^-
FADH₂ E ^$\circ$ ' = -0.22 V