Deck 14: Electron Transport, Oxidative Phosphorylation, and Oxygen Metabolism

Question 1

Which of the following is NOT involved in the enzymatic inactivation of reactive oxygen species?

A) Superoxide dismutase
B) Catalase
C) Vitamin C
D) Peroxiredoxin
E) Peroxidase

Answer 1

C

Question 2

________, which are potentially damaging, are generated because the interactions between one electron and two electron carriers are not 100% efficient.

Answer 2

Reactive oxygen species

Question 3

Which of the following is NOT true of respiratory control?

A) Oxidative phosphorylation is absolutely dependent on the continued flow of electrons from substrates to oxygen.
B) Oxidative phosphorylation is regulated by allosteric mechanisms.
C) The stimulation of respiration by addition of ADP is stoichiometric.
D) The rate of respiration is controlled by the balance between the △G's for phosphorylation of ADP, electron transport and proton pumping.
E) Maintenance of respiratory control depends on the structural integrity of the mitochondrial inner membrane.

Answer 3

B

Question 4

Electron transport through NADH-Coenzyme Q reductase (Complex I) is accompanied by transfer of ________ protons from the matrix to the intermembrane space.

Question 5

Which of the following is NOT an electron acceptor in the mitochondrial respiratory chain?

A) FMN
B) FAD
C) Fe3+
D) Cu2+
E) CoQH2

Question 6

CoQ carries electrons from NADH-Coenzyme Q reductase and succinate dehydrogenase as well as other flavoproteins to CoQ:Cytochrome c oxidoreductase.

Question 7

All of the cytochromes in the mitochondrial respiratory chain contain the same heme moiety as found in hemoglobin.

Question 8

In animal cells the mitochondrial electron transport chain is responsible for reoxidizing most of the NADH produced by oxidative pathways regardless of the cellular compartment in which it was produced.

Question 9

Electrons are transferred through the respiratory chain from reduced NADH or FADH2 to oxygen in small steps with each step in the pathway associated with a slightly more ________ reduction potential.

Question 10

Calculate the free energy change associated with transporting one proton from the matrix to the intermembrane space at 37∘C where the electrical potential across the membrane is ~ = 170 mV and the △pH is +0.75.

Question 11

Which of the following statements about oxidative phosphorylation by ATP synthase is FALSE?

A) The electrochemical gradient across the inner mitochondrial membrane generated by electron flow is used to synthesize ATP.
B) Uncouplers dissipate the electrochemical gradient but electron transport continues without ATP production.
C) Inhibitors disrupt electron flow as well as ATP synthesis.
D) A proton gradient alone without a corresponding energy input is not sufficient to drive the synthesis of ATP.
E) ATP synthesis occurs via simultaneous conformational changes in protein subunits containing catalytic sites.

Question 12

The ATP yield from NADH transported across the mitochondrial inner membrane by the glycerol phosphate shuttle is the same as if the malate/aspartate shuttle were used.

Question 13

Calculate the standard free energy change for the reactionFADH2 + 1/2O2 → FAD + H2O given that the standard reduction potential for the reduction of oxygen to water is +0.82 V and for the reduction of FAD to FADH2 is +0.03 V.

Question 14

The Q cycle is responsible for transferring electrons from a two-electron donor ________ to a one-electron acceptor ________ at the point of complex III of the mitochondrial respiratory chain.

Question 15

Energy derived from oxidation of acetyl-CoA in the citric acid cycle is used for the production of ________ in brown adipose tissue because the mitochondria are rich in UCP1.

Question 16

Proton-driven rotation of the c-ring of the F0 unit of the F1F0 ATP synthase is required for complete passage of protons from the intermembrane space to the matrix.

Question 17

Calculate the efficiency of energy conversion from glucose under aerobic conditions assuming that 32 moles of ATP are produced for each mole of glucose and given that △G0' for glucose oxidation is -2870kJ/mol and the △G0' for ATP hydrolysis is -32.2 kJ/mol.

Question 18

Which of the following statements is FALSE?

A) All of the protein complexes of the mitochondrial respiratory chain are bound in the inner mitochondrial membrane.
B) Cytochrome c and coenzyme Q are both soluble electron carriers that are loosely attached to the outside of the inner mitochondrial membrane.
C) Oxygen is reduced to water at complex IV of the mitochondrial respiratory chain.
D) The citric acid cycle is linked directly to the mitochondrial respiratory chain at the site of complex II.
E) During electron transport protons are pumped across the inner mitochondrial membrane from the matrix to the intermembrane space.

Question 19

Oligomycin is an inhibitor of ADP phosphorylation because it blocks the flow of protons through the ________.