Deck 20: Electron Transport and Oxidative Phosphorylation

Question 1

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

Answer 1

H⁺ to H₂ gas.

Question 2

Which of the following terms describes ATP synthesis in mitochondria?

A) substrate-level phosphorylation
B) oxidative phosphorylation
C) photophosphorylation
D) none of these

Answer 2

oxidative phosphorylation

Question 3

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

Answer 3

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

Question 4

How many electrons are required for the complete reduction of one molecule of oxygen gas?

A) one
B) two
C) four
D) eight

Question 5

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

Question 6

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

Question 7

Which of the following is not a part of the electron transport chain?

A) NADH
B) FADH₂
C) coenzyme Q
D) coenzyme A

Question 8

The final reduced species in the electron transport chain is

A) O₂
B) H₂O
C) cytochrome c
D) coenzyme Q
E) none of these

Question 9

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 Δ G ° by a well known equation.
D) It cannot be determined for electron-transfer reactions involving coenzyme Q.

Question 10

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

Question 11

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

Question 12

The ultimate electron acceptor in the electron transport chain is

A) NAD⁺.
B) FAD.
C) oxygen.
D) ADP.
E) none of these

Question 13

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

Question 14

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

Question 15

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

Question 16

The pH of the mitochondrial matrix is ____ the pH of the intermembrane space.

A) higher than
B) lower than
C) the same as

Question 17

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

Question 18

To calculate the Δ G 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

Question 19

Which of the following is an advantage of using multiple steps in electron transport?

A) By using several steps the net − Δ G 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.

Question 20

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.

Question 21

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.

Question 22

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.

Question 23

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

Question 24

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

Question 25

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.

Question 26

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.

Question 27

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.

Question 28

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.

Question 29

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

Question 30

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.

Question 31

The cytochrome that passes electrons directly to oxygen is

A) the cytochrome a\a ₃ complex.
B) cytochrome b .
C) cytochrome c .
D) cytochrome c _1.

Question 32

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.

Question 33

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.

Question 34

A cytochrome that can move freely in the mitochondrial membrane is

A) cytochrome a
B) cytochrome b
C) cytochrome c
D) cytochrome c ₁

Question 35

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

Question 36

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.

Question 37

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.

Question 38

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.

Question 39

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.

Question 40

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

Question 41

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.

Question 42

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

Question 43

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

Question 44

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.

Question 45

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.

Question 46

The factor that couples electron transport to phosphorylation of ADP is

A) a protein oligomer
B) a protein monomer
C) gramicidin A
D) valinomycin

Question 47

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

Question 48

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

Question 49

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.

Question 50

Brown adipose tissue is partially responsible for generating heat in the young human body.

Question 51

Conformation changes in proteins are crucial in the synthesis of ATP in the mitochondria.

Question 52

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

Question 53

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

Question 54

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

Question 55

The F₁F₀ complex is actually a transmembrane complex.

Question 56

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

Question 57

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

Question 58

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

Question 59

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.

Question 60

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

Question 61

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

Question 62

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.

Question 63

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

Question 64

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

Question 65

​ 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

Question 66

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

Question 67

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.

Question 68

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

Question 69

Explain the formation of a proton gradient.

Question 70

​ Cytochromes are groups of proteins containing a _____ group.

A) heme
B) hemin
C) corrin
D) chlorin

Question 71

​ 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