Test Bank - Lehninger Principles of Biochemistry, 7th, and 8th
Edition by Nelson, All Chapters
Almost all of the oxygen (O2) one consumes in breathing is converted to:
A) acetyl-CoA.
B) carbon dioxide (CO2).
C) carbon monoxide and then to carbon dioxide.
D) none of the above.
E) water. - ANSWER: E) water.
A new compound isolated from mitochondria is claimed to represent a previously unrecognized
carrier in the electron transfer chain. It is given the name coenzyme Z. Which line of evidence do
you feel is the least conclusive in assigning this compound a position in the electron transfer chain?
A) Alternate oxidation and reduction of the mitochondrion-bound coenzyme Z can be readily
demonstrated.
B) Removal of coenzyme Z from the mitochondria results in a decreased rate of oxygen
consumption.
C) The rate of oxidation and reduction of mitochondrion-bound coenzyme is of the same order of
magnitude as the overall rate of electron transfer in mitochondria as measured by oxygen
consumption.
D) The reduction potential of Z is between that of two compounds known to participate in the
electron transport chain
E) When added to a mitochondrial suspension, coenzyme Z is taken up very rapidly and specifically
by the mitochondria. - ANSWER: E) When added to a mitochondrial suspension, coenzyme Z is taken
up very rapidly and specifically
by the mitochondria.
Antimycin A blocks electron transfer between cytochromes b and c1. If intact mitochondria were
incubated with antimycin A, excess NADH, and an adequate supply of O2, which of the following
would be found in the oxidized state?
A) Coenzyme Q
B) Cytochrome a3
C) Cytochrome b
D) Cytochrome e
E) Cytochrome f - ANSWER: B) Cytochrome a3
Cyanide, oligomycin, and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic
phosphorylation. Which of the following statements correctly describes the mode of action of the
three inhibitors?
A) Cyanide and 2,4-dinitrophenol inhibit the respiratory chain, and oligomycin inhibits the
synthesis of ATP.
B) Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-dinitrophenol inhibit the
synthesis of ATP.
C) Cyanide, oligomycin, and 2,4-dinitrophenol compete with O2 for cytochrome oxidase (Complex
IV).
D) Oligomycin and cyanide inhibit synthesis of ATP; 2,4-dinitrophenol inhibits the respiratory
chain.
E) Oligomycin inhibits the respiratory chain, whereas cyanide and 2,4-dinitrophenol prevent the
synthesis of ATP. - ANSWER: B) Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-
dinitrophenol inhibit the
, synthesis of ATP.
In the reoxidation of QH2 by purified ubiquinone-cytochrome c reductase (Complex III) from heart
muscle, the overall stoichiometry of the reaction requires 2 mol of cytochrome c per mole of QH2
because:
A) cytochrome c is a one-electron acceptor, whereas QH2 is a two-electron donor.
B) cytochrome c is a two-electron acceptor, whereas QH2 is a one-electron donor.
C) cytochrome c is water soluble and operates between the inner and outer mitochondrial
membranes
D) heart muscle has a high rate of oxidative metabolism, and therefore requires twice as much
cytochrome c as QH2 for electron transfer to proceed normally.
E) two molecules of cytochrome c must first combine physically before they are catalytically active. -
ANSWER: B) cytochrome c is a two-electron acceptor, whereas QH2 is a one-electron donor.
If electron transfer in tightly coupled mitochondria is blocked (with antimycin A) between
cytochrome b and cytochrome c1, then:
A) all ATP synthesis will stop.
B) ATP synthesis will continue, but the P/O ratio will drop to one.
C) electron transfer from NADH will cease, but O2 uptake will continue.
D) electron transfer from succinate to O2 will continue unabated.
E) energy diverted from the cytochromes will be used to make ATP, and the P/O ratio will rise. -
ANSWER: A) all ATP synthesis will stop.
In normal mitochondria, the rate of NADH consumption (oxidation) will:
A) be increased in active muscle, decreased in inactive muscle.
B) be very low if the ATP synthase is inhibited, but increase when an uncoupler is added.
C) decrease if mitochondrial ADP is depleted.
D) decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3
complex.
E) All of the above are true. - ANSWER: E) All of the above are true.
Which of the following statements about the chemiosmotic theory is correct?
A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one
side of the inner mitochondrial membrane.
B) It predicts that oxidative phosphorylation can occur even in the absence of an intact inner
mitochondrial membrance.
C) The effect of uncoupling reagents is a consequence of their ability to carry electrons through
membranes.
D) The membrane ATP synthase has no significant role in the chemiosmotic theory.
E) All of the above are correct. - ANSWER: A) Electron transfer in mitochondria is accompanied by an
asymmetric release of protons on one
side of the inner mitochondrial membrane.
Which of the following statements about the chemiosmotic theory is false?
A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one
side of the inner mitochondrial membrane.
B) Energy is conserved as a transmembrane pH gradient.
C) Oxidative phosphorylation cannot occur in membrane-free preparations.
D) The effect of uncoupling reagents is a consequence of their ability to carry protons through
membranes.
E) The membrane ATPase, which plays an important role in other hypotheses for energy coupling,
has no significant role in the chemiosmotic theory. - ANSWER: E) The membrane ATPase, which plays
an important role in other hypotheses for energy coupling,
Edition by Nelson, All Chapters
Almost all of the oxygen (O2) one consumes in breathing is converted to:
A) acetyl-CoA.
B) carbon dioxide (CO2).
C) carbon monoxide and then to carbon dioxide.
D) none of the above.
E) water. - ANSWER: E) water.
A new compound isolated from mitochondria is claimed to represent a previously unrecognized
carrier in the electron transfer chain. It is given the name coenzyme Z. Which line of evidence do
you feel is the least conclusive in assigning this compound a position in the electron transfer chain?
A) Alternate oxidation and reduction of the mitochondrion-bound coenzyme Z can be readily
demonstrated.
B) Removal of coenzyme Z from the mitochondria results in a decreased rate of oxygen
consumption.
C) The rate of oxidation and reduction of mitochondrion-bound coenzyme is of the same order of
magnitude as the overall rate of electron transfer in mitochondria as measured by oxygen
consumption.
D) The reduction potential of Z is between that of two compounds known to participate in the
electron transport chain
E) When added to a mitochondrial suspension, coenzyme Z is taken up very rapidly and specifically
by the mitochondria. - ANSWER: E) When added to a mitochondrial suspension, coenzyme Z is taken
up very rapidly and specifically
by the mitochondria.
Antimycin A blocks electron transfer between cytochromes b and c1. If intact mitochondria were
incubated with antimycin A, excess NADH, and an adequate supply of O2, which of the following
would be found in the oxidized state?
A) Coenzyme Q
B) Cytochrome a3
C) Cytochrome b
D) Cytochrome e
E) Cytochrome f - ANSWER: B) Cytochrome a3
Cyanide, oligomycin, and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic
phosphorylation. Which of the following statements correctly describes the mode of action of the
three inhibitors?
A) Cyanide and 2,4-dinitrophenol inhibit the respiratory chain, and oligomycin inhibits the
synthesis of ATP.
B) Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-dinitrophenol inhibit the
synthesis of ATP.
C) Cyanide, oligomycin, and 2,4-dinitrophenol compete with O2 for cytochrome oxidase (Complex
IV).
D) Oligomycin and cyanide inhibit synthesis of ATP; 2,4-dinitrophenol inhibits the respiratory
chain.
E) Oligomycin inhibits the respiratory chain, whereas cyanide and 2,4-dinitrophenol prevent the
synthesis of ATP. - ANSWER: B) Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-
dinitrophenol inhibit the
, synthesis of ATP.
In the reoxidation of QH2 by purified ubiquinone-cytochrome c reductase (Complex III) from heart
muscle, the overall stoichiometry of the reaction requires 2 mol of cytochrome c per mole of QH2
because:
A) cytochrome c is a one-electron acceptor, whereas QH2 is a two-electron donor.
B) cytochrome c is a two-electron acceptor, whereas QH2 is a one-electron donor.
C) cytochrome c is water soluble and operates between the inner and outer mitochondrial
membranes
D) heart muscle has a high rate of oxidative metabolism, and therefore requires twice as much
cytochrome c as QH2 for electron transfer to proceed normally.
E) two molecules of cytochrome c must first combine physically before they are catalytically active. -
ANSWER: B) cytochrome c is a two-electron acceptor, whereas QH2 is a one-electron donor.
If electron transfer in tightly coupled mitochondria is blocked (with antimycin A) between
cytochrome b and cytochrome c1, then:
A) all ATP synthesis will stop.
B) ATP synthesis will continue, but the P/O ratio will drop to one.
C) electron transfer from NADH will cease, but O2 uptake will continue.
D) electron transfer from succinate to O2 will continue unabated.
E) energy diverted from the cytochromes will be used to make ATP, and the P/O ratio will rise. -
ANSWER: A) all ATP synthesis will stop.
In normal mitochondria, the rate of NADH consumption (oxidation) will:
A) be increased in active muscle, decreased in inactive muscle.
B) be very low if the ATP synthase is inhibited, but increase when an uncoupler is added.
C) decrease if mitochondrial ADP is depleted.
D) decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3
complex.
E) All of the above are true. - ANSWER: E) All of the above are true.
Which of the following statements about the chemiosmotic theory is correct?
A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one
side of the inner mitochondrial membrane.
B) It predicts that oxidative phosphorylation can occur even in the absence of an intact inner
mitochondrial membrance.
C) The effect of uncoupling reagents is a consequence of their ability to carry electrons through
membranes.
D) The membrane ATP synthase has no significant role in the chemiosmotic theory.
E) All of the above are correct. - ANSWER: A) Electron transfer in mitochondria is accompanied by an
asymmetric release of protons on one
side of the inner mitochondrial membrane.
Which of the following statements about the chemiosmotic theory is false?
A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one
side of the inner mitochondrial membrane.
B) Energy is conserved as a transmembrane pH gradient.
C) Oxidative phosphorylation cannot occur in membrane-free preparations.
D) The effect of uncoupling reagents is a consequence of their ability to carry protons through
membranes.
E) The membrane ATPase, which plays an important role in other hypotheses for energy coupling,
has no significant role in the chemiosmotic theory. - ANSWER: E) The membrane ATPase, which plays
an important role in other hypotheses for energy coupling,
