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Test Bank For Lehninger Principles of Biochemistry 8th Edition By David L
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Test Bank For Lehninger Principles of Biochemistry 8thEdition By David L. Nelson; Michael M. Cox All
Chapters 1-28 LATES
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,
has no significant role in the chemiosmotic theory.
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