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Biochemistry > Electron Transport Chain > Flashcards

Electron Transport Chain 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. the pH of the matrix is greater than the pH of the intermembrane space.

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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. The synthesis of ATP is directly linked to the oxidation of NADH

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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. higher than

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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. oxidative phosphorylation

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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. oxygen.

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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. four

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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. It is measured by comparison with the partial pressure of oxygen in the bloodstream rather than 1 atmosphere pressure

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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. H+ to H2 gas.

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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. True

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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. all of these

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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. More energy can be captured to synthesize ATP by using small steps.

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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. cytochrome c; O2; pumps

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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. coenzyme Q; cytochrome c; pumps

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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. cytochrome C

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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. FADH2; coenzyme Q; doesn’t pump

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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. NADH; coenzyme Q; pumps

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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. H2O

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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. coenzyme A

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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. Complex IV

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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. coenzyme Q to cytochrome c via Complex III.

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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. in the oxidized, reduced, and semiquinone
forms.

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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. all the components of the electron transport chain and one of the components of the citric acid cycle, namely the succinate dehydrogenase complex

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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. succinate to fumarate.

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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. succinate-CoQ
oxidoreductase.

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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. the cytochrome a/a3 complex.

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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. cytochrome 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. cytochrome c oxidase.

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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. coenzyme Q.

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. cytochrome b and cytochrome 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. on the inner membrane.

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

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

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. NADH-CoQ oxidoreductase.

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. Cytochrome bc1 complex.

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. Complex II

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. True

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. Complex IV

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. Complex IV.

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. Cytochrome A oxidase.

40
Q

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

A

a. True

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. use of respiratory inhibitors

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. Complex II

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. without affecting electron transport.

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. Complexes I, III, and IV

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.
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.

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. a protein oligomer

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. oxygen atoms consumed in electron transport

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. Stopping ATP synthesis but not stopping electron flow

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. Uncoupling agents can work by disrupting the flow of protons during ATP synthesis

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. submitochondrial preparations that contain closed vesicles can carry out oxidative phosphorylation

51
Q

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

A

a. True

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. Using a proton gradient to synthesize ATP.

53
Q

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

A

a. True

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. the release of tightly bound ATP from the synthase

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. iron-sulfur proteins bind to the ATP synthase

56
Q

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

A

a. True

57
Q

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

A

a. True

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. The transfer of electrons from complex I to oxygen was shown

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. True

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. it shuttles the electrons from NADH across the mitochondrial membrane to FADH2, yielding 5 ATP/NADH

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. True

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. 30 − 32, dependent on the shuttle system used.

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. different shuttle mechanisms operate to transfer electrons from the cytosol to the
mitochondrion in the two sets of tissues

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. True

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. muscle creatine-phosphate

66
Q

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

A

b. False

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. Inner mitochondrial membrane

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. reduction potential

69
Q

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

A

a. heme

Biochemistry (14 decks)

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