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Biochemistry > Electron Transport and Oxidative Phosphorylation > Flashcards

Electron Transport and Oxidative Phosphorylation Flashcards

1
Q

When mitochondria are actively carrying out aerobic respiration
a. the pH of the matrix is greater than the pH of the intermembrane space.
b. the pH of the matrix is less than the pH of the intermembrane space.
c. the pH of the matrix is about the same as the pH of the intermembrane space.
d. the pH of the matrix versus the intermembrane space has nothing to do with whether not aerobic respiration is
occurring.

A

a

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2
Q

Which of the following is not true?
a. The synthesis of ATP in mitochondria is driven by a proton or pH gradient.
b. The synthesis of ATP is directly linked to the oxidation of NADH
c. The reoxidation of NADH and FADH2 indirectly creates a proton gradient that is involved in ATP synthesis
d. All of these are true

A

b

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3
Q

The pH of the mitochondrial matrix is ____ the pH of the intermembrane space.
a. higher than
b. lower than
c. the same as

A

a

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4
Q

Which of the following terms describes ATP synthesis in mitochondria?
a. substrate-level phosphorylation
b. oxidative phosphorylation
c. photophosphorylation
d. none of these

A

b

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5
Q

The ultimate electron acceptor in the electron transport chain is
a. NAD+.
b. FAD.
c. oxygen.
d. ADP.
e. none of these

A

c

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6
Q

How many electrons are required for the complete reduction of one molecule of oxygen gas?
a. one
b. two
c. four
d. eight

A

c

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7
Q

Which of the following statements concerning E° for an electron-transfer reaction is false?
a. It is measured by comparison with the partial pressure of oxygen in the bloodstream rather than 1 atmosphere
pressure.
b. It is measured by comparison with a standard hydrogen electrode.
c. It is related to ΔG° by a well known equation.
d. It cannot be determined for electron-transfer reactions involving coenzyme Q.

A

a

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8
Q

The reference reaction for determining reduction potentials (E° = 0) is the reduction of
a. oxygen (O2) to water.
b. NAD+
to NADH.
c. H+ to H2 gas.
d. FAD to FADH2.
e. none of these

A

c

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9
Q

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

A

a

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10
Q

To calculate the ΔG of a redox reaction, you need:
a. the reduction potential (E°) of the half reactions
b. the Faraday constant
c. the number of electrons involved in the transfer
d. none of these
e. all of these

A

e

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11
Q

Which of the following is an advantage of using multiple steps in electron transport?
a. By using several steps the net −ΔG is higher (more energy is released).
b. More heat can be generated by using small steps.
c. More energy can be captured to synthesize ATP by using small steps.
d. Small steps allow for both more heat generation and more ATP synthesis.
e. All of these statements are advantages of using multiple steps.

A

c

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12
Q

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

a. coenzyme Q; cytochrome c; pumps
b. cytochrome c; coenzyme Q; pumps
c. cytochrome c; O2; doesn’t pump
d. cytochrome c; O2; pumps

A

d

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13
Q

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

a. coenzyme Q; cytochrome c; pumps
b. coenzyme Q; cytochrome c; doesn’t pump
c. cytochrome c; coenzyme Q; pumps
d. cytochrome c; coenzyme Q; doesn’t pump

A

a

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14
Q

Which of the following components of the electron transport chain can only participate in one-electron transfers?
a. NAD
b. FAD
c. coenzyme Q
d. cytochrome C

A

d

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15
Q

Complex II of the electron transport chain oxidizes ____, reduces ____, and ____ protons in the process.
a. FADH2; coenzyme Q; doesn’t pump
b. FADH2; coenzyme Q; pumps
c. NADH; coenzyme Q; doesn’t pump
d. NADH; coenzyme Q; pumps

A

a

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16
Q

Complex I of the electron transport chain oxidizes ____, reduces ____, and ____ protons in the process.
a. FADH2; coenzyme Q; doesn’t pump
b. FADH2; coenzyme Q; pumps
c. NADH; coenzyme Q; doesn’t pump
d. NADH; coenzyme Q; pumps

A

d

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17
Q

The final reduced species in the electron transport chain is
a. O2
b. H2O
c. cytochrome c
d. coenzyme Q
e. none of these

A

b

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18
Q

Which of the following is not a part of the electron transport chain?
a. NADH
b. FADH2
c. coenzyme Q
d. coenzyme A

A

d

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19
Q

Which complex of the electron transport chain does NOT contain an iron-sulfur cluster?
a. Complex I
b. Complex II
c. Complex III
d. Complex IV

A

d

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20
Q

The Q cycle refers to flow of electrons from
a. NADH to coenzyme Q via Complex I.
b. FADH2 to coenzyme Q via Complex II.
c. coenzyme Q to cytochrome c via Complex III.
d. coenzyme Q to NADH.
e. none of these

A

c

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21
Q

In the Q cycle coenzyme Q takes part
a. in the oxidized and reduced forms only.
b. in the oxidized, reduced, and semiquinone forms.
c. in the oxidized and semiquinone forms only.
d. in the reduced and semiquinone forms only.

A

b

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22
Q

Which of the following are located in the inner mitochondrial membrane?
a. all the components of the citric acid cycle and the electron transport chain
b. all the components of the citric acid cycle but none of the components of the electron transport chain
c. all the components of the electron transport chain but none of the components of the citric acid cycle
d. all the components of the electron transport chain and one of the components of the citric acid cycle, namely
the succinate dehydrogenase complex

A

d

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23
Q

An alternative mode of entry into the electron transport chain is the oxidation of
a. malate to oxalosuccinate.
b. succinate to fumarate.
c. isocitrate to α-ketoglutarate.
d. α-ketoglutarate to succinyl-CoA.

A

b

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24
Q

Another name for Complex II in the electron transport chain is
a. cytochrome c oxidase.
b. NADH-CoQ oxidoreductase.
c. cytochrome bc1 complex.
d. succinate-CoQ oxidoreductase.

A

d

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25
Q

The cytochrome that passes electrons directly to oxygen is
a. the cytochrome a/a3 complex.
b. cytochrome b.
c. cytochrome c.
d. cytochrome c1

A

a

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26
Q

A cytochrome that can move freely in the mitochondrial membrane is
a. cytochrome a
b. cytochrome b
c. cytochrome c
d. cytochrome c1

A

c

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27
Q

The complex in the electron transport chain that does not have a direct link to coenzyme Q in some form is
a. the succinate dehydrogenase complex.
b. Complex I.
c. cytochrome c oxidase.
d. Complex III.

A

c

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28
Q

A species in the electron transport chain that can participate in a two-electron transfer is
a. iron-sulfur proteins.
b. cytochrome b.
c. cytochrome c.
d. coenzyme Q.

A

d

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29
Q

Iron deficiency in a cell can adversely affect electron transport at which of the following sites?
a. coenzyme Q and FADH2
b. NADH and FADH2
c. cytochrome b and cytochrome c
d. coenzyme Q and NADH

A

c

30
Q

Most of the reactions of electron transport in the mitochondria occur
a. on the outer membrane
b. on the inner membrane.
c. in the mitochondrial matrix.
d. in the intermembrane space.
e. in the cytosol.

A

b

31
Q

Electron flow in the mitochondria follows this pathway:

a. NADH → FMN → Coenzyme Q → Cyt A → Cyt B → Cyt C → O2

b. NADH → FMN → Cyt B → Coenzyme Q → Cyt C → Cyt A → O2

c. FMNH2 → NAD → Coenzyme Q → Cyt B → Cyt C → Cyt A → O2

d. NADH → FMN → Coenzyme Q → Cyt B → Cyt C → Cyt A → O2

e. NADH → FMN → Cyt B → Cyt C → Coenzyme Q → Cyt A → O2

A

d

32
Q

Electron flow in the mitochondria follows this pathway:

a. Complex I → complex II → complex III → complex IV.

b. Complex IV → complex III → complex II → complex I.

c. Complex I → complex III → complex IV.

d. Complex II → complex III → complex IV.

e. Both complex I → III → IV and complex II → III → IV.

A

e

33
Q

Another name for Complex I in the mitochondria is
a. Cytochrome C oxidase.
b. NADH-CoQ oxidoreductase.
c. succinate-CoQ reductase.
d. Cytochrome A oxidase.
e. Cytochrome bc1 complex.

A

b

34
Q

Another name for Complex III in the mitochondria is
a. Cytochrome C oxidase.
b. NADH-CoQ reductase.
c. succinate-CoQ reductase.
d. Cytochrome A oxidase.
e. Cytochrome bc1 complex.

A

e

35
Q

Which complex contains succinate dehydrogenase?
a. Complex I
b. Complex II
c. Complex III
d. Complex IV
e. It is not known where succinate dehydrogenase is located.

A

b

36
Q

Coenzyme Q can act as an intermediate electron carrier, since the ketone group of the quinone structure is readily
reduced to an alcohol.
a. True
b. False

A

a

37
Q

Which complex contains cytochrome oxidase?
a. Complex I
b. Complex II
c. Complex III
d. Complex IV
e. It is not known where cytochrome oxidase is located.

A

d

38
Q

The only complex which actually uses molecular oxygen is
a. Complex I.
b. Complex II.
c. Complex III.
d. Complex IV.
e. It is not known where oxygen is used.

A

d

39
Q

The only reaction which actually uses molecular oxygen is catalyzed by
a. Cytochrome C oxidase.
b. NADH-CoQ reductase.
c. succinate-CoQ reductase.
d. Cytochrome A oxidase.
e. Cytochrome bc1 complex.

A

d

40
Q

Transition metals are especially important in electron transport, since they have variable oxidation states.
a. True
b. False

A

a

41
Q

Which of the following procedures is most unique to the determination of the order of the passage of electrons through
the electron transport chain was determined
a. use of respiratory inhibitors
b. spectroscopy
c. isolation of intact mitochondria
d. none of these have anything to do with determining the order

A

a

42
Q

Which of the following complexes does not directly contribute to the production of ATP by pumping protons?
a. Complex I.
b. Complex II.
c. Complex III.
d. Complex IV.
e. All four complexes pump protons.

A

b

43
Q

Uncouplers are compounds that inhibit the phosphorylation of ADP
a. by enhancing the proton gradient across the outer mitochondrial membrane.
b. by enhancing the proton gradient across the inner mitochondrial membrane.
c. because they are transmembrane proteins in the outer mitochondrial membrane.
d. without affecting electron transport.

A

d

44
Q

Oxidative phosphorylation is coupled to electron transport in
a. Complexes I, II, and III
b. Complexes I, II, and IV
c. Complexes I, III, and IV
d. all four respiratory complexes

A

c

45
Q

How do uncoupling agents affect the electron transport chain and oxidative phosphorylation?
a. They block the flow of electrons, so protons aren’t pumped, and ATP synthesis ceases.
b. They remove electrons from the chain, so less protons are pumped, and ATP synthesis decreases.
c. They block the flow of protons through the ATP synthase, so ATP synthesis ceases. Electron flow and proton
pumping are also halted as a result.
d. They provide an alternative path for protons to re-enter the mitochondrial matrix, so ATP synthesis decreases. Electron flow and proton pumping are not affected.

A

d

46
Q

The factor that couples electron transport to phosphorylation of ADP is
a. a protein oligomer
b. a protein monomer
c. gramicidin A
d. valinomycin

A

a

47
Q

The P/O ratio refers to the number of moles of ATP produced for each mole of
a. oxygen atoms consumed in electron transport
b. oxygen molecules consumed in electron transport
c. NADH reoxidized in electron transport
d. FADH2 reoxidized in electron transport

A

a

48
Q

Uncoupling in mitochondria refers to:
a. Interruption of electron flow.
b. Stopping electron flow but not stopping ATP synthesis.
c. Stopping ATP synthesis but not stopping electron flow.
d. Blocking the electrons from NADH from entering the electron transport system.
e. All of these describe uncoupling.

A

c

49
Q

Which of the following is true?
a. Uncoupling agents can work by disrupting the flow of protons during ATP synthesis.
b. Uncoupling agents prevent the flow of electrons during electron transport
c. Uncoupling agents always block the flow of protons through the ATPase
d. none of these is true

A

a

50
Q

Evidence for chemiosmotic coupling as the mechanism for oxidative phosphorylation is based on the observation that
a. mitochondrial membrane fragments without compartmentalization can carry out oxidative phosphorylation
b. submitochondrial preparations that contain closed vesicles can carry out oxidative phosphorylation
c. many different kinds of substances can serve as uncouplers
d. it has proved impossible to duplicate the process in model systems

A

b

51
Q

Brown adipose tissue is partially responsible for generating heat in the young human body.
a. True
b. False

A

a

52
Q

Chemiosmotic coupling involves this process:
a. Using an electron gradient to synthesize ATP.
b. Using a proton gradient to synthesize ATP.
c. Using oxygen flow to synthesize ATP.
d. Using a proton gradient to make water from oxygen.
e. These are all chemiosmotic processes.

A

b

53
Q

The F1F0 complex is actually a transmembrane complex.
a. True
b. False

A

a

54
Q

In the conformational coupling mechanism for oxidative phosphorylation, the effect of the proton gradient is
a. to inhibit conformational changes in the ATP synthase
b. to create more sites for ATP synthesis
c. the release of tightly bound ATP from the synthase
d. all of these
e. none of these

A

c

55
Q

Which of the following is not true of the process of oxidative phosphorylation?
a. protons flow into the mitochondrial matrix through ion channels in the ATP synthase
b. the F0 part of the ATP synthase serves as a proton channel
c. the F1 part of the ATP synthase is the site of ATP formation
d. iron-sulfur proteins bind to the ATP synthase

A

d

56
Q

Conformation changes in proteins are crucial in the synthesis of ATP in the mitochondria.
a. True
b. False

A

a

57
Q

Chemiosmotic coupling was first proposed by Peter Mitchell, who won a Nobel Prize for his theory.
a. True
b. False

A

a

58
Q

Which of the following was not evidence that supported Mitchell’s chemiosmotic coupling hypothesis?
a. Closed vessicles were required. Phosphorylation did not occur in a completely soluble environment.
b. Vessicles could be prepared from mitochondria and the assymetric location of electron transport protein could
be shown.
c. The existence of the pH gradient could be demonstrated
d. The transfer of electrons from complex I to oxygen was shown
e. none of these

A

d

59
Q

Mitochondrial membranes can be fragmented into small vesicles which still synthesize ATP; intact mitochondria are
not required.
a. True
b. False

A

a

60
Q

A characteristic of the glycerol phosphate shuttle is
a. it shuttles NADH across the mitochondrial membrane to yield 5 ATP/NADH
b. it shuttles the electrons from NADH across the mitochondrial membrane to FADH2, yielding 5 ATP/NADH
c. it only operates efficiently at high levels of NADH
d. malate is a key component in the shuttle process

A

b

61
Q

Depending on how NADH is shuttled from the cytoplasm into the mitochondria, different molar amounts of ATP will
be synthesized as each NADH is oxidized.
a. True
b. False

A

a

62
Q

What is the net yield of ATP per glucose molecule that passes through all of aerobic respiration (glucose → CO2 +
H2O)?
a. 2
b. 4
c. 6
d. 30 − 32, dependent on the shuttle system used.

A

d

63
Q

The yield of ATP from the complete oxidation of glucose is lower in muscle and brain from that in kidney, liver, and
heart because
a. there are fewer mitochondria in muscle and brain cells
b. muscle and brain cells have a lower requirement for ATP
c. different shuttle mechanisms operate to transfer electrons from the cytosol to the mitochondrion in the two sets
of tissues
d. none of the above

A

c

64
Q

Most athletes make better aerobic use of energy sources than non-athletes, since they actually have more mitochondria
in their cells.
a. True
b. False

A

a

65
Q

If a cyclist started a race and rode at a near maximum speed, which of the following fuel sources would be used up
first?
a. fat in the muscle cells
b. muscle glycogen
c. liver glycogen
d. muscle creatine-phosphate
e. all of these would be exhausted simultaneously

A

d

66
Q

Creatine supplements work best for long distance exercise, rather than for quick spurts of energy.
a. True
b. False

A

b

67
Q

Which part of mitochondria develops a proton gradient as a result of electron transport?
a. Outer mitochondrial membrane
b. Inner mitochondrial membrane
c. Cristae
d. Matrix

A

b

68
Q

In an electron transport chain, the standard voltage that indicates the tendency of a reduction half reaction to take place
is called _____.
a. reduction coefficient
b. reduction standard
c. reduction potential
d. standard potential

A

c

69
Q

Cytochromes are groups of proteins containing a _____ group.
a. heme
b. hemin
c. corrin
d. chlorin

A

a

70
Q

Explain the formation of a proton gradient.

A

A proton gradient exists because the various proteins that serve as electron carriers in the
respiratory chain are (a) not symmetrically oriented in relation to the two sides of the inner
mitochondrial membrane or (b) they do not react in the same manner with respect to the matrix and the intermembrane space. In the process of electron transport, the proteins of the respiratory
complexes take up protons from the matrix to transfer them in redox reactions; these electron
carriers subsequently release protons into the intermembrane space when they are reoxidized,
creating the proton gradient. As a result, there is a higher concentration of protons in the
intermembrane space than in the matrix

71
Q

Explain how uncouplers, dinitrophenol and valinomycin differ from one another.

A

The conjugate base of dinitrophenol acid (i.e., dinitrophenolate anion) is the actual uncoupler because it can react with protons in the intermembrane space, reducing the difference in proton
concentration between the two sides of the inner mitochondrial membrane. However, valinomycin
is also an ionophore. It creates a channel through which ions such as H+, K+, and Na+ can pass
through the membrane.

Biochemistry (21 decks)

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