CH 18

1 point

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 spectroscopic analysis is performed,

the coenzyme Q pool will be found in both oxidized & reduced states, and cytochrome c will be found in only one state.

the coenzyme Q pool will be found in only one state, and cytochrome c will be found in both oxidized & reduced states.

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

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

both the coenzyme Q pool and cytochrome c will be found in both oxidized & reduced states.

1 point

A poison that prevents the transfer of electrons from the last FeS cluster of Complex I to coenzyme Q is added to a suspension of actively respiring mitochondria. Which of the following will be observed?

This poison would have little to no effect on ATP production.

ATP production would be severely impaired as this would completely block electron transport through the electron transport chain.

ATP production would be severely impaired as this poison would directly inhibit the ATP synthase, of which coenzyme Q is a subunit.

ATP production would be reduced as fewer protons would be pumped out of the mitochondrial matrix.

ATP production would be impaired as this would uncouple oxidative phosphorylation from electron transport.

1 point

Cytochrome c oxidase forms a transient radical at a _____ side chain adjacent to the heme a3- ligated O2.

serine

tryptophan

phenylalanine

threonine

tyrosine

1 point

Which of the following energy sources drives the phosphate carrier that transports Pi into the mitochondria from the cytosol?

ATP hydrolysis

simultaneous transport of H+ out of the mitochondrion

simultaneous transport of H+ into the mitochondrion

simultaneous transport of ATP out of the mitochondrion

simultaneous transport of ADP into the mitochondrion

1 point

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 only

I, II, III, IV

II, III, IV

III, IV

I, II, III

1 point

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.

II only

I, II, III

I, II

II, III, IV

I only

1 point

What is the net result of the successive reactions catalyzed by superoxide dismutase and catalase?

Conversion of the free radical O2– to H2O2, which is converted to water and O2.

Conversion of the free radical O2– to H2O2, which is converted to water and GSSG.

Conversion of the free radical O2– to peroxide, which is converted to CO2.

Conversion of the free radical O2– to carbon dioxide and water.

none of the above

1 point

Which of the following statements are true about oxidative phosphorylation?

Electron transport provides energy to pump protons into the intermembrane space.

An electrochemical gradient is formed across the inner mitochondrial membrane.

Potassium and sodium ions form an ionic gradient across the inner mitochondrial membrane.

A and B

A, B, and C

1 point

Which statement concerning the mitochondrial F0F1 ATP synthase is false?

The F0 unit binds the antibiotic oligomycin.

The F1 subunit undergoes conformational changes as it binds substrate, catalyses the synthesis of ATP and releases the product.

The F1 subunit includes four sets of αβ dimers.

The F0 subunit includes a ring of between 9 & 12 proton-carrying polypeptides.

None of the above; they’re all true.

10.

1 point

Several prosthetic groups act as redox centers in Complex I, including

FMN, ubiquinone, iron-sulfur clusters, heme.

FMN, ubiquinone, iron-sulfur clusters.

heme, ubiquinone, iron-sulfur clusters.

all of the above

none of the above

11.

1 point

Which statement concerning Complex II of the electron transport chain is false?

This complex oxidizes FADH2 and reduces coenzyme Q.

This complex also oxidizes succinate to fumarate in the TCA cycle.

This complex includes a cytochrome heme.

This complex includes Fe-S centers.

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

12.

1 point

How many electrons can be carried by the prosthetic group in cytochrome?

1 or 2

none of the above

13.

1 point

Cyanide (CN-) inhibits electron transport at

Complex I

Complex III

Complex IV

Complex II

Coenzyme Q

14.

1 point

The electrons formed from the oxidation of glucose are

directly transferred to O2 during the citric acid cycle.

transferred to the coenzymes NAD+ and FAD.

transferred to succinate and arachidonic acid.

A and B

none of the above

16.

1 point

How many ATP molecules are synthesized by the aerobic metabolism of one glucose molecule in eukaryotes?

17.

1 point

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.

FAD, [2Fe-2S], [4Fe-4S], Heme b560

Heme b560, [2Fe-2S], [4Fe-4S], FAD

ubiquinone, [4Fe-4S], [2Fe-2S], FMN

FMN, Heme b560, [2Fe-2S], CoQ

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

18.

1 point

Rotenone and amytal inhibit electron transport at

Complex III

Complex II

Complex I

Coenzyme Q

Complex IV

19.

1 point

Newborns generate heat by nonshivering thermogenesis that occurs in ______ tissue.

muscle

pancreatic

liver

white adipose tissue

brown adipose (fat)

20.

1 point

Which complex is unable to generate sufficient free energy to power ATP synthesis?

Complex I

Complex II

Complex III

Complex IV

All the complexes are able to generate sufficient free energy.

21.

1 point

Oxidative phosphorylation is regulated by

the availability of reduced cofactors from catabolic pathways.

the availability of the dNTPs.

the availability of ADP and Pi.

A and C

A, B, and C

22.

1 point

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.-.

I only

I, II

I, III, IV

III only

III, IV

23.

1 point

Which of the following best describes the function of cytochrome c oxidase?

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

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

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

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

24.

1 point

Which of the following best explains why heme groups are often buried within protein structures?

Hemes are very hydrophobic and require surrounding proteins for solubility in aqueous solution.

Hemes are very hydrophilic and require surrounding proteins for solubility in lipid membranes.

Proteins increase the reactivity of hemes so that they can more rapidly transfer electrons.

Proteins protect the heme and prevent it from indiscriminately transferring electrons, thus controlling the target and rate of electron transfer.

25.

1 point

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.

I, II, III

II, III

II only

III, IV

I, II, III, IV

26.

1 point

Consider the following half-reactions:
εo′=–0.315V NAD+ +H+ +2e– ↔NADH
εo′ = 0.815 V 1/2 O2 + 2 H+ + 2 e– ↔ H2O

What is the εo′ for the following redox equation?
NAD+ +H+ +2e– ↔NADH
1/2O2 +NADH+H+ →H2O+NAD+

–1.13 V

–0.5 V

+0.5 V

+1.13 V

none of the above

27.

1 point

How many ATP molecules are synthesized from the oxidation of 1 NADH molecule?

2.5

1.5

28.

1 point

Which of the following are true statements about the structure of ATP synthase?

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

The γ subunit acts as a “cam” shaft in the rotational motor.

The structure has a “lollipop” shape.

A and B

A, B, and C

29.

1 point

How many different oxidation states can FMN adopt in the electron transport chain?

30.

1 point

Some degenerative diseases, such as Parkinson’s disease, are associated with oxidative damage to ______.

golgi apparatus

nuclei

endoplasmic reticulum

mitochondria

31.

1 point

The functional core of Complex III includes:

cytochrome c1, iron-sulfur protein (Rieske).

cytochrome c1, cytochrome b, myoglobin.

cytochrome c1, cytochrome b, iron-sulfur protein (Rieske).

all of the above

none of the above

32.

1 point

Antimycin A inhibits electron transport at

Complex II

Coenzyme Q

Complex I

Complex IV

Complex III

33.

1 point

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?

Add a second blocking agent to interfere with either Complex I or Complex II along with the poison

Add an artificial electron donor along with the poison.

None of the above will help distinguish between these two possibilities.

There is no justification to come to that conclusion in the first place.

Add an uncoupling agent along with the poison.

34.

1 point

How many mitochondria does a typical eukaryotic cell contain?

2000

20000

200000

35.

1 point

Which of the following statements about the mitochondrial inner membrane is FALSE?

The inner membrane contains about 75% protein.

The inner membrane contains many respiratory proteins.

The inner membrane is permeable to CO2, H2O, and small ions.

The inner membrane is highly invaginated.