BIOCHEM 4412 CH. 18 Electron Transport and Oxidative Phosphorylation

A 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 Option A: ATP production would be reduced due to a decrease in the number of protons pumped out of the mitochondrial matrix. B Option B: ATP production would be impaired due to the uncoupling of oxidative phosphorylation from electron transport. C Option C: ATP production would be maintained at the normal rate due to functional overlap between Complex I and Complex II. D Option D: ATP production would be halted completely due to the block in electron transport through the electron transport chain. E Option E: ATP production would be reduced due to inhibition of the CoQ subunit of ATP synthase.

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

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 Option A: Add an uncoupling agent along with the poison. B Option B: Any of the above would allow differentiation between these two possibilities. C Option C: Add a second blocking agent to interfere with either Complex I or Complex II along with the poison. D Option D: Add an artificial electron donor along with the poison. E Option E: None of the above will help distinguish between these two possibilities.

A Option A: Add an uncoupling agent along with the poison.

Why is the exchange of ATP for ADP by the ADP-ATP translocator electrogenic? A Option A: Because the net charge of ATP is more negative than that of ADP B Option B: Because the concentration of ATP is much less than that of ADP in the matrix C Option C: Because the net charge of ATP is more positive than that of ADP D Option D: Because the concentration of ATP is much greater than that of ADP in the matrix

A Option A: Because the net charge of ATP is more negative than that of ADP

Which statement(s) concerning the mitochondrial F0-F1 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. A Option A: I only B Option B: II, III C Option C: None of the options (I - III) is false. D Option D: I, II, III E Option E: III only

A Option A: I only

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. A Option A: II, III, IV B Option B: II only C Option C: I, II, III, IV D Option D: I, II, III E Option E: III, IV

A Option A: II, III, IV

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. A Option A: III only B Option B: I, II C Option C: II, III D Option D: II only E Option E: IV only

A Option A: III only

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

A Option A: oxaloacetate

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

A Option A: simultaneous transport of H+ into the mitochondrion.

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

A Option A: spontaneously due to the redox potential gradient.

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

A Option A: the rotation of the γ subunit.

Rotation of a subunit in the catalytic portion of ATP synthase has been directly observed. A Option A: True B Option B:False

A Option A: True

The amount of ATP present at any one time in the body is about 0.1 mol even though the average woman uses over 200 mol per day. A Option A: True B Option B:False

A Option A: True

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. A Option A: II only B Option B: I only C Option C: I, III D Option D: II, III E Option E: I, II, III

B Option B: I only

Molecules that prevent oxidative damage by the superoxide radical possess ______ properties.

Antioxidants

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

B Option B: 3; 1 or 2

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

B Option B: Complex II; Complex I

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

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

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. A Option A: I only B Option B: I, II C Option C: I, II, III D Option D: II only E Option E: II, III, IV

B Option B: I, II

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. A Option A: I, IV B Option B: I, II C Option C: I, II, III, IV D Option D: II, III, IV E Option E: II, IV

B Option B: I, II

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. A Option A: IV only B Option B: I, II, III C Option C: II, III, IV D Option D: I, II, III, IV E Option E: III only

B Option B: I, II, III

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. A Option A: I, III B Option B: I, II, III, IV C Option C: II, IV D Option D: I, III, IV. E Option E: I, II

B Option B: I, II, III, IV

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. A Option A: I, II, III, IV B Option B: II, III, IV C Option C: II, III D Option D: III only E Option E: I, II, III

B Option B: II, III, IV

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. A Option A: III, IV B Option B: II, III, IV C Option C: I, II, III, IV D Option D: II only E Option E: I, II, III

B Option B: II, III, IV

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 Option A: the coenzyme Q pool will be found in only one state, and cytochrome c will be found in both oxidized & reduced states. B Option B: the coenzyme Q pool will be found in the reduced state, and cytochrome c will be found in the oxidized state. C Option C: the coenzyme Q pool will be found in the oxidized state, and cytochrome c will be found in the reduced state. D Option D: both the coenzyme Q pool and cytochrome c will be found in both oxidized & reduced states. E Option E: the coenzyme Q pool will be found in both oxidized & reduced states, and cytochrome c will be found in only one state.

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

Aerobic metabolism is only slightly more efficient than anaerobic glycolysis. A Option A: True B Option B:False

B Option B:False

Oxidation of NADH and FADH2 is carried out by the electron transport chain, a set of protein complexes containing redox centers with decreasing standard reduction potentials. A Option A: True B Option B:False

B Option B:False

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

E Option E: 2.5

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

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

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

C Option C: 2000

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

C Option C: 32

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. A Option A: II, IV B Option B: II, III, IV C Option C: I, II, IV D Option D: I, III, IV E Option E: II, III

C Option C: I, II, IV

Which property is necessary for a molecule such as DNP to function as a typical uncoupler of oxidative phosphorylation? A Option A: Lipophilic alcohol B Option B: Hydrophilic weak acid C Option C: Lipophilic weak acid D Option D: Hydrophilic strong acid

C Option C: Lipophilic weak acid

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 Option A: None of the above B Option B: coenzyme Q C Option C: cytochrome c D Option D: Fe-S E Option E: 2Fe-2S

C Option C: cytochrome c

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

E Option E: CoQ

Complexes I and II each transfer electrons to ______.

Coenzyme Q

Cytochrome c oxidase contains four redox centers: two heme groups and two redox centers containing_______.

Copper

Which conformation of the active sites in ATP synthase allows binding of substrates? (could be multiple answers) A Option A : T state B Option B : O state C Option C : C state D Option D : L state

D Option D : L state

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. A Option A: I, II, IV B Option B: II, III, IV C Option C: II, III D Option D: I, III, IV E Option E: II, IV

D Option D: I, III, IV

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. A Option A: III, IV B Option B: I, II, III, IV C Option C: II only D Option D: II, III E Option E: I, II, III

D Option D: II, 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.-. A Option A: I, II B Option B: I, III, IV C Option C: I only D Option D: III only E Option E: III, IV

D Option D: III only

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

E Option E: 2.5

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

E Option E: CoQ

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. A Option A: I only B Option B: II, III, IV C Option C: I, III, IV D Option D: I, III E Option E: III only

E Option E: III only

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 Option A: UCP-1; muscle B Option B: thermogenin; muscle C Option C: UCP-1; white adipose D Option D: UCP-2; brown adipose E Option E: thermogenin; brown adipose

E Option E: thermogenin; brown adipose

The cytochromes within complex III all contain _____ groups.

Heme

The inner mitochondrial membrane divides the mitochondrion into the inner membrane space and the ______.

Matrix

Bacteria carry out electron transport in the _____.

Plasma Membrane

The stoichiometric relationship of ATP synthesis to ______ is referred to as the P/O ratio.

Respiration

Electrons from cytosolic NADH are transferred to the matrix via electron ______ systems.

Shuttle