CHAPTER 18: ELECTRON TRANSPORT AND OXIDATIVE PHOSPHORYLATION

Phosphate (Pi) is transported into the mitochondria from the cytosol by a phosphate carrier which is driven by the A: simultaneous transport of ATP out of the mitochondrion. B: simultaneous transport of H+ into the mitochondrion. C: hydrolysis of ATP. D: simultaneous transport of H+ out of the mitochondrion. E: simultaneous transport of ADP into the mitochondrion

B: simultaneous transport of H+ into the mitochondrion.

In the electron transport chain, FMN can adopt ____ oxidation state(s) and is capable of accepting or donating ____ electron(s). A: 3; 1 or 2 B: 3; 2 C: 2; 2 D: 3; 1 E: 2; 1 or 2

A: 3; 1 or 2

Bacteriorhodopsin is an example of a light-driven ______ . A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

B: proton pump

Protons moving through a transmembrane channel by "jumping" through an arrangement of hydrogen-bonded groups are described as moving through a proton ______. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

D: wire

Consider the following half-reactions: ℰ°' = -0.315 V NAD+ + H+ + 2 e- ↔ ADH ℰ°' = 0.815 V 1/2 O2 + 2 H+ + 2 e- ↔ H2O What is the ℰ°' for the following redox equation? O2 + 2 NADH + 2 H+ → 2 H2O + 2 NAD+ A: -1.130 V B: none of the above C: -0.500 V D: +0.500 V E: +1.130 V

E: +1.130 V

Approximately how many ATP molecules are synthesized from the oxidation of 1 NADH? A: 1.5 B: 2 C: 1 D: 3 E: 2.5

E: 2.5

Electrons from FADH2 are delivered to ____ and electrons from NADH are delivered to ____ of the electron transport chain. A: Complex I; Complex II B: Complex I; Complex IV C: Complex I; Complex III D: Complex II; Complex III E: Complex II; Complex I

E: Complex II; Complex I

Molecules that prevent oxidative damage by the superoxide radical possess ______ properties. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

G: antioxidant

Cytochrome c oxidase contains four redox centers: two heme groups and two redox centers containing_______. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

H: copper

A typical eukaryotic cell contains up to ____ mitochondria each bound by a smooth outer membrane. A: 200,000 B: 2000 C: 20 D: 20,000 E: 2

B: 2000

Based on the estimation presented in the chapter, how many ATP per glucose are synthesized by the aerobic metabolism in eukaryotes? A: 60 B: 32 C: 4 D: 38 E: 2

B: 32

Redox Centers in order of favorable electron flow:

Most negative to most positive

poison that prevents the transfer of electrons from the last [Fe-S] cluster of Complex I to coenzyme Q is added to a suspension of actively respiring mitochondria. Which of the following will be observed? A: ATP production would be reduced due to a decrease in the number of protons pumped out of the mitochondrial matrix. B: ATP production would be reduced due to inhibition of the CoQ subunit of ATP synthase. C: ATP production would be halted completely due to the block in electron transport through the electron transport chain. D: ATP production would be maintained at the normal rate due to functional overlap between Complex I and Complex II. E: ATP production would be impaired due to the uncoupling of oxidative phosphorylation from electron transport.

A: ATP production would be reduced due to a decrease in the number of protons pumped out of the mitochondrial matrix.

Electrons from cytosolic NADH are transferred to the matrix via electron ______ systems. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

A: shuttle

The structure of ATP synthase changes in conformation as a result of A: the rotation of the γ subunit. B: the rotation of the α and β subunits. C: the rotation of the β subunit. D: the rotation of ATP. E: all of the above.

A: the rotation of the γ subunit.

Which of the following is TRUE regarding heme proteins? I. Heme groups are capable of transferring electrons across large distances provided that some molecular network exists as a "path." II. Heme groups are often buried in protein structure because the protein protects the heme and prevents it from indiscriminately transferring electrons. III. The rate of electron transfer from a reduced heme is physiologically significant. IV. Heme groups are often differentiated by their absorption spectrum.

All of above: I. Heme groups are capable of transferring electrons across large distances provided that some molecular network exists as a "path." II. Heme groups are often buried in protein structure because the protein protects the heme and prevents it from indiscriminately transferring electrons. III. The rate of electron transfer from a reduced heme is physiologically significant. IV. Heme groups are often differentiated by their absorption spectrum.

One method used by newborn mammals to generate heat is referred to as nonshivering thermogenesis. This method utilizes a protein channel called ________ which is present in high levels inside the mitochondria of _____tissue. A: UCP-1; white adipose B: thermogenin; brown adipose C: UCP-2; brown adipose D: UCP-1; muscle E: thermogenin; muscle

B: thermogenin; brown adipose

Which conformation of the active sites in ATP synthase allows binding of substrates? A : C state B : O state C : L state D : T state

C : L state

Which of the following best describes the function of cytochrome c oxidase? A: Cytochrome c oxidase oxidizes four consecutive cytochrome c molecules, via one-electron transfers, while simultaneously reducing two O2 to two H2O. B: Cytochrome c oxidase oxidizes two consecutive cytochrome c molecules, via two-electron transfers, while simultaneously reducing one O2 to two H2O. C: Cytochrome c oxidase oxidizes four consecutive cytochrome c molecules, via one-electron transfers, while simultaneously reducing one O2 to two H2O. D: Cytochrome c oxidase oxidizes two consecutive cytochrome c molecules, via two- electron transfers, while simultaneously reducing two O2 to two H2O.

C: Cytochrome c oxidase oxidizes four consecutive cytochrome c molecules, via one-electron transfers, while simultaneously reducing one O2 to two H2O.

Which of the following are TRUE statements regarding the structure of ATP synthase? A : The γ ubunit acts as the proton "wire" allowing equilibration of the ion gradient. B: Research indicates that the F1 portion of the protein rotates in a circular counterclockwise direction. C: It has a membrane-embedded component called F0 and a component found in the matrix referred to as F1.

C: It has a membrane-embedded component called F0 and a component found in the matrix referred to as F1.

Complexes I and II each transfer electrons to ______. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

C: coenzyme Q

Cyclonite is a poison that blocks electron transfer between cytochromes bL and bH. When this poison is added to a suspension of isolated mitochondria, and when spectroscopic analysis is performed, A: the coenzyme Q pool will be found in only one state, and cytochrome c will be found in both oxidized & reduced states. B: both the coenzyme Q pool and cytochrome c will be found in both oxidized & reduced states. C: the coenzyme Q pool will be found in the reduced state, and cytochrome c will be found in the oxidized state. D: the coenzyme Q pool will be found in the oxidized state, and cytochrome c will be found in the reduced state. E: the coenzyme Q pool will be found in both oxidized & reduced states, and cytochrome c will be found in only one state.

C: the coenzyme Q pool will be found in the reduced state, and cytochrome c will be found in the oxidized state.

The effects of a poison on actively respiring mitochondria are being studied to determine its mode of action. When the poison is added, every component of the electron transport chain is found to be in its reduced form based on spectroscopic analysis, and ATP production ceases entirely. It is reasoned that the poison is either blocking the final transfer of electrons to oxygen or is blocking the ATP synthase. Which of the following experiments will help unravel this dilemma? A: None of the above will help distinguish between these two possibilities. B: Any of the above would allow differentiation between these two possibilities. C: Add an artificial electron donor along with the poison. D: Add an uncoupling agent along with the poison. E: Add a second blocking agent to interfere with either Complex I or Complex II along with the poison.

D: Add an uncoupling agent along with the poison.

Which of the prosthetic groups listed can accept or donate either one or two electrons due to the stability of the semiquinone state? A: NADH B: Rieske center C: [2Fe-2S] D: CoQ E: cytochrome c

D: CoQ

Which of the following correctly ranks redox centers found in Complex I from lower to higher potential? A correct answer will contain redox centers which are found in only Complex I and will also rank those redox centers in order of lower to higher reduction potential. A: FMN, Heme b560, [2Fe-2S], CoQ B: Heme b560, [2Fe-2S], [4Fe-4S], FAD C: FAD, [2Fe-2S], [4Fe-4S], Heme b560 D: FMN, [2Fe-2S], [4Fe-4S] E: ubiquinone, [4Fe-4S], [2Fe-2S], FMN

D: FMN, [2Fe-2S], [4Fe-4S]

What is the net result of the successive reactions catalyzed by superoxide dismutase and catalase? A: conversion of the free radical O2· to H2O2, which is converted to water and GSSG and water B: conversion of the free radical O2· to carbon dioxide and water C: conversion of the free radical O2· to peroxide, which is converted to CO2 and water D: conversion of the free radical O2· to H2O2, which is converted to water and O2 E: none of the above

D: conversion of the free radical O2· to H2O2, which is converted to water and O2

In a newly discovered electron transport complex a researcher has identified the redox center Fe-S, cytochrome c, and coenzyme Q. The researcher also knows that this complex ultimately passes its electrons to oxygen. What is most likely the redox center which completes this task? A: coenzyme Q B: 2Fe-2S C: None of the above D: cytochrome c E: Fe-S

D: cytochrome c

Some degenerative diseases, such as Parkinson's disease, are associated with ______ damage to ______. A: oxidative; nuclei B: thermogenic; mitochondria C: thermogenic; nuclei D: oxidative; mitochondria E: free radical; nuclei

D: oxidative; mitochondria

In the electron transport chain, electrons are passed from redox center to redox center ____. A: in an ATP dependent fashion. B: with the assistance of a carrier protein. C: as a result of the proton gradient. D: spontaneously due to the redox potential gradient. E: as a result of the addition of free energy.

D: spontaneously due to the redox potential gradient.

In theory how many protons could be pumped under standard state conditions by Complex III per mol of CoQ oxidized, considering the following information? (NOTE: mt = mitochondria) coenzyme Q + 2H+ + 2 e- → coenzyme QH2 ℰ°' ≈ 0.040 V cytochrome c (Fe3+) + e- → cytochrome c (Fe2+) ℰ° ≈ 0.270 V H+ (outside mt) → H+ (inside mt) ΔG ≈ -20 kJ/mol Faraday constant (F) ≈ 100 kJ/V mol ∆Gº' = -nF∆E0' A: greater than six protons but less than or equal to eight protons B: greater than 8 protons C: Cannot be determined from the information provided. D: four or less protons E: greater than four protons but less than or equal to six protons

E: greater than four protons but less than or equal to six protons

The cytochromes within complex III all contain _____ groups. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

E: heme

All of the following inhibit electron transport EXCEPT A: cyanide B: All of the above inhibit electron transport C: anitimycin A D: rotenone E: oxaloacetate

E: oxaloacetate

According to the proposed reaction sequence presented in the chapter, cytochrome c oxidase obtains a fourth electron from a ____ residue adjacent to the heme a3-ligated O2, thus forming a transient radical. A: phenylalanine B: serine C: tryptophan D: threonine E: tyrosine

E: tyrosine

The stoichiometric relationship of ATP synthesis to ______ is referred to as the P/O ratio. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

F: respiration

Which of the following statements is(are) TRUE about oxidative phosphorylation? I. Electron transport provides energy to pump protons into the intermembrane space. II. An electrochemical gradient is formed across the inner mitochondrial membrane. III. Potassium and sodium ions form an ionic gradient across the inner mitochondrial membrane. IV. Complexes I, II, III, IV actively transport protons into the intermembrane space during electron transport.

I. Electron transport provides energy to pump protons into the intermembrane space. II. An electrochemical gradient is formed across the inner mitochondrial membrane.

Which statement(s) concerning the mitochondrial F0F1 ATP synthase is FALSE? I. The F1 subunit includes rotating sets of αβ dimers. II. The F0 subunit includes a ring of between 9 and 12 proton-carrying polypeptides. III. The F1 subunit undergoes a series of conformational changes throughout the course of reaction.

I. The F1 subunit includes rotating sets of αβ dimers.

An animal with the UCP-1 protein would I. generate excess heat. II. have lower energy levels. III. generate ATP efficiently via oxidative phosphorylation.

I. generate excess heat. II. have lower energy levels.

Rotenone and amytal I. inhibition can be restored by addition of succinate. II. inhibition can be restored by addition of cytochrome c. III. blocks consumption of oxygen. IV. blocks transfer of electrons from CoQ to Complex III.

I. inhibition can be restored by addition of succinate. II. inhibition can be restored by addition of cytochrome c. III. blocks consumption of oxygen.

The rate of oxidative phosphorylation I. is regulated by the availability of ADP and Pi. II. is reduced when the ratio of [NADH]/[NAD+] is high. III. increases with a higher concentration of reduced cytochrome c IV. is regulated by activity of the ADP-ATP translocator.

I. is regulated by the availability of ADP and Pi. III. increases with a higher concentration of reduced cytochrome c IV. is regulated by activity of the ADP-ATP translocator.

The electrons formed from the aerobic oxidation of glucose are I. ultimately transferred to O2 after several other transfer reactions. II. transferred to the coenzymes NAD+ and FAD. III. directly transferred to O2 during the citric acid cycle. IV. transferred to succinate and arachidonic acid.

I. ultimately transferred to O2 after several other transfer reactions. II. transferred to the coenzymes NAD+ and FAD.

ATP forms (is produced) I. upon transition from the loose to the tight form of the α and β subunit complex of ATP synthase. II. as a result of the flux of electrons through the channel formed by Fo III. as a result of the positive ions pumped into the matrix of the mitochondrion.

I. upon transition from the loose to the tight form of the α and β subunit complex of ATP synthase.

Which of the following is TRUE regarding the complexes within the electron transport system? I. Complex II contributes twice as many protons to the gradient than Complex I II. Inhibition of Complex II would decrease the total number of electrons moving through the electron transport chain. III. Inhibition of Complex II would not alter the amount of free energy generated from electrons originating from NADH. IV. Complex I can accept electrons with higher potential than Complex II is able to accept.

II. Inhibition of Complex II would decrease the total number of electrons moving through the electron transport chain. III. Inhibition of Complex II would not alter the amount of free energy generated from electrons originating from NADH.

Which of the following statements about the mitochondrial inner membrane is TRUE? I. The inner membrane is permeable to CO2, H2O, and small ions. II. The inner membrane contains several transport proteins and membrane bound enzymes. III. In general, a higher inner membrane surface area correlates to a higher rate of respiration. IV. The number of cristae reflects the respiratory activity of the cell.

II. The inner membrane contains several transport proteins and membrane bound enzymes. III. In general, a higher inner membrane surface area correlates to a higher rate of respiration. IV. The number of cristae reflects the respiratory activity of the cell.

___ the gradient with the synthesis of ATP via oxidative phosphorylation. I. The Fo portion of ATP synthase II. Thermogenin uncouples III. 2,4-dinitrophenol (DNP) dissipates IV. An ionophore capable of transporting potassium ions across the membrane

II. Thermogenin uncouples III. 2,4-dinitrophenol (DNP) dissipates

Antimycin A I. inhibition can be restored by addition of succinate. II. inhibition can be restored by addition of cytochrome c. III. blocks consumption of oxygen. IV. blocks transfer of electrons from CoQ to Complex III.

II. inhibition can be restored by addition of cytochrome c. III. blocks consumption of oxygen. IV. blocks transfer of electrons from CoQ to Complex III.

Based on the information in the chapter, which of the following is TRUE regarding Complex III? I. A large portion of Complex III dissociates from the membrane bound portion of the complex. II. Complex III contains three identical cytochrome redox centers. III. The Q cycle allows stepwise reoxidation of the two electrons from CoQH2. IV. A change in conformation of iron sulfur protein (ISP) ensures that the Reiske center is reduced preferentially by CoQ.-.

III. The Q cycle allows stepwise reoxidation of the two electrons from CoQH2.

Which statement concerning Complex II of the electron transport chain is FALSE? I. This complex oxidizes FADH2 and reduces coenzyme Q. II. This complex includes the covalently bound enzyme succinate dehydrogenase. III. This complex pumps protons from the matrix to the intermembrane space. IV. This complex also oxidizes succinate to fumarate in the citric acid cycle.

III. This complex pumps protons from the matrix to the intermembrane space.

Cyanide (CN-) I. inhibition can be restored by addition of succinate. II. inhibition can be restored by addition of cytochrome c. III.inhibits electron transport which stops consumption of oxygen. IV. blocks transfer of electrons from CoQ to Complex III.

III.inhibits electron transport which stops consumption of oxygen.

The inner mitochondrial membrane divides the mitochondrion into the inner membrane space and the ______. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

J: matrix

Bacteria carry out electron transport in the _____. A: shuttle B: proton pump C: coenzyme Q D: wire E: heme F: respiration G: antioxidant H: copper I: cytosol J: matrix K: tunnel L: plasma membrane

L: plasma membrane