Chapter 20—Electron Transport and Oxidative Phosphorylation
MULTIPLE CHOICE
1. ATP made in glycolysis and the TCA cycle is the result of ____ phosphorylation, and NADH-
dependent ATP synthesis is the result of ____ phosphorylation.
a.
oxidative; substrate-level
b.
oxidative; electron
c.
substrate-level; electron
d.
substrate-level; oxidative
e.
proton-gradient; oxidative
2. Reduction involves the ____ of electron(s), and reactions for which the standard cell potential is ____
are spontaneous under standard conditions.
a.
loss; negative
b.
loss; positive
c.
gain; negative
d.
gain; positive
e.
none of the above
3. Spontaneity of a redox reaction depends upon each of the following EXCEPT:
a.
standard cell potential
b.
concentration of the species being oxidized
c.
concentration of the species being reduced
d.
a and b only
e.
a, b, and c
4. Where does the energy that drives ATP synthesis come from?
a.
The proton gradient.
b.
NAD+ and FAD.
c.
The electron gradient.
d.
The oxidation states of the complexes.
e.
Molecular oxygen.
5. All of the following are in the mitochondria EXCEPT:
a.
enzymes for fatty acid oxidation.
b.
adenylate kinase.
c.
creatine kinase.
d.
the electron transport complexes.
e.
pentose phosphate pathway.
6. All are characteristics of inner mitochondrial membranes EXCEPT:
a.
contains specific transport proteins.
b.
membrane lipids have mostly unsaturated fatty acids.
c.
folds into cristae.
d.
contains porin in high concentration.
e.
all are correct.
7. Each of the following is a true statement EXCEPT:
a.
standard free energy change for a redox reaction is related to the standard cell potential
b.
standard free energy change for a redox reaction is related to the number of electrons
transferred
c.
for redox reactions with negative standard cell potentials, standard free energy change is
negative
d.
redox reactions must occur in pairs, where the total number of electrons involved in the
oxidation equals the total number involved in the reduction
e.
all are true statements
8. Each of the following regarding redox couples is true EXCEPT:
a.
standard reduction potentials are measured relative to a standard hydrogen cell (H+/H2)
b.
for cells in which electrons flow toward the sample half-cell, the reduction potential is
positive
c.
a redox couple consists of a substance being oxidized, and the substance oxidizing it
d.
a half-reaction involving the loss of electrons is an oxidation reaction
e.
all are true statements.
9. Compounds with a large ____ reduction potential have a strong tendency to undergo oxidation, and as
such, NADH is a strong ____ agent.
a.
positive; oxidizing
b.
negative; reducing
c.
negative; oxidizing
d.
positive; reducing
e.
can’t be determined from information given
10. All of the following are membrane bound EXCEPT:
a.
cytochrome a/a3.
b.
Fe−S centers.
c.
cytochrome c.
d.
cytochrome c1.
e.
coenzyme Q.
11. All are linked to the electron-transport chain through Complex I accepting electrons from NADH
EXCEPT:
a.
gluconeogenesis.
b.
glycolysis.
c.
TCA cycle.
d.
fatty acid oxidation.
e.
all are true.
12. Complex I and Complex II produce a common product which is:
a.
NAD+.
b.
FAD.
c.
reduced coenzyme Q.
d.
reduced cyt c.
e.
reduced O2.
13. All are flavoproteins EXCEPT:
a.
NADH-CoQ reductase (complex I).
b.
succinate dehydrogenase (complex II).
c.
coenzyme Q-cytochrome c oxidoreductase (complex III).
d.
sn-glycerolphosphate dehydrogenase.
e.
fatty acyl-CoA dehydrogenase-transferring protein.
14. Which complex reduces molecular oxygen?
a.
complex I
b.
complex II
c.
complex III
d.
UQH/UQH2 pool
e.
complex IV
15. Complex I contains all of these components EXCEPT:
a.
[FMN].
b.
2Fe−2S clusters.
c.
4Fe−4S clusters.
d.
cytochrome c.
e.
“proton pump.”
16. Which of the following is a two-electron donor?
a.
FAD
b.
Fe−S
c.
NADH
d.
NAD+
e.
cyt c
17. All of the following are properties of coenzyme Q EXCEPT:
a.
hydrophobic.
b.
can easily diffuse in the membrane.
c.
shuttle from complex I and complex II to complex IV.
d.
isoprenoid tail.
e.
three oxidation states.
18. The first half of the Q cycle results in which of the following?
a.
transfer of 4 protons to the intermembrane space
b.
a semiquinone racical (UQ•–) in the Qn site
c.
2 molecules of reduced cytochrome c
d.
return of one UQH2 to the coenzyme Q pool
e.
none of the above
19. All of the following take place in the Q cycle EXCEPT:
a.
transfer of electrons from bL to bH.
b.
an electron is passed from bL to UQ.
c.
an electron is passed from bH to UQ.
d.
one UQH2 is returned to the pool.
e.
two protons are pumped into the matrix.
20. Which of the following is/are mobile electron carrier(s)?
A.
UQ
B.
Cyt c
C.
Complex III
a.
A only
b.
B only
c.
C only
d.
B & C
e.
A & B
21. Complex III takes up ____ proton(s) on the matrix side of the ____ membrane and releases ____
protons on the intermembrane side for each pair of ____ passed through the Q cycle.
a.
two; inner; four; electrons
b.
one; inner; two; protons
c.
two; inner; four; protons
d.
one; outer; two; electrons
e.
none are true
22. All are single-electron carriers EXCEPT:
a.
UQH2.
b.
Cyt bL.
c.
Cyt bH.
d.
Rieske protein Fe−S clusters.
e.
Cyt c1.
23. The final electron acceptor in the electron transport chain is:
a.
molecular oxygen.
b.
H2O.
c.
cytochrome c.
d.
UQ.
e.
NAD+.
24. All are characteristics of cyt c EXCEPT:
a.
accepts electrons from cyt c1.
b.
water soluble.
c.
globular with planar heme group near the center of the protein.
d.
heme iron coordinated with histidine nitrogen and methionine sulfur atoms.
e.
all are true.
25. All are components of cytochrome c oxidase (complex IV) EXCEPT:
a.
CuA.
b.
CuB.
c.
Cyt c1.
d.
Cyt a3.
e.
Cyt a.
26. The complete reduction of one molecule of oxygen gas requires how many electrons?
a.
two
b.
three
c.
four
d.
eight
e.
six
27. Another name for complex II (succinate dehydrogenase) in the electron transport chain is:
a.
cytochrome c oxidase.
b.
NADH-CoQ reductase.
c.
succinate-CoQ reductase.
d.
cytochrome c reductase.
e.
cytochrome bc1 complex.
28. What molecule is the electron donor to complex III?
a.
cytochrome c
b.
UQH2
c.
NADH
d.
H2O
e.
FADH2
29. All of the following transfer electrons to the UQ/UQH2 pool EXCEPT:
a.
fatty acyl-CoA dehydrogenase.
b.
sn-glycerolphosphate dehydrogenase.
c.
Complex I.
d.
Complex II.
e.
Complex IV.
30. Which of the following complex(es) translocate protons in the inner mitochondrial membrane?
a.
complexes I, II, and IV
b.
complexes I, III, and IV
c.
complexes I and IV
d.
complexes III and IV
e.
complexes I, II, III, and IV
31. All are characteristics of the binuclear center of complex IV EXCEPT:
a.
water is released here.
b.
CuB is a component.
c.
Cyt a3 is a component.
d.
Two electrons are transferred to bound O2.
e.
Fe−S is a component.
32. The model of electron transport includes all EXCEPT:
a.
mobile coenzyme Q collecting electrons.
b.
four independent mobile complexes.
c.
cyt c moving in the intermembrane space.
d.
protons driven into the matrix.
e.
proton gradient generated to produce ATP.
33. All of the following are properties of ATP synthase EXCEPT:
a.
the F1 subunit is attached to the integral membrane protein F0.
b.
the F0 subunit is hydrophilic.
c.
transmembrane channel for protons.
d.
beta-subunits have the catalytic site for ATP synthesis.
e.
the ring of c subunits form a rotor with respect to the alpha subunits.
34. All are true for F1 unit of ATP synthase EXCEPT:
a.
consists of five different kinds of subunits.
b.
catalyzes ATP hydrolysis as well as ATP synthesis.
c.
-subunits have catalytic sites for ATP synthesis.
d.
– and -subunits are homologous.
e.
all are true.
35. In ATP synthase, the ____ subunit is the site of ATP synthesis while the ____ subunit forms the proton
channel through the inner mitochondrial membrane.
a.
; a
b.
;
c.
c
d.
c
e.
a;
36. All are characteristics of the binding charge mechanism EXCEPT:
a.
one site is empty (O-sites).
b.
one site contains ADP and Pi (L–sites).
c.
T-sites become O-sites.
d.
energy-driven conformational changes convert O-sites to L-sites.
e.
T-sites bind ATP.
37. Characteristics of proton gradient driven enzyme conformational change in ATP synthase include all
EXCEPT:
a.
binding of substrates.
b.
ATP synthesis.
c.
catalytic cooperativity between subunits.
d.
conformational change in the -subunits releasing ATP.
e.
()3 complex rotates relative to a fixed -subunit.
38. The hypothesis for proton driven ATP synthesis depends on proton neutralization of the negative
charge on c-subunit ____ residues as the rotor turns. This causes the ____-subunit to turn relative to
the three ____-subunits.
a.
Ser; c;
b.
Ser; b;
c.
Asp; ;
d.
Arg; c;
e.
Asp; ;
39. Which complex will be affected if rotenone is added?
a.
complex I
b.
complex II
c.
complex III
d.
complex IV
e.
none, it is an uncoupler
40. Does electron transport stop if rotenone is added? Why?
a.
Yes, there is not an electron source.
b.
No, rotenone is not strong enough to inhibit all of the electron transport chain.
c.
No, there is still a source of electrons from Complex II.
d.
Yes, rotenone inhibits complex III, therefore, electrons can not be passed on.
e.
Can not be determined from the information given.
41. Which of the following is an inhibitor of Complex IV?
a.
rotenone
b.
oligomycin
c.
antimycin
d.
cyanide
e.
all of the above
42. Cyanide and azide bind tightly to the ferric form of ____, and carbon monoxide toxicity arises from its
affinity for the iron of ____.
a.
cyt c; cyt a3
b.
cyt a3; hemoglobin
c.
hemoglobin; hemoglobin
d.
myoglobin; hemoglobin
e.
cyt a; cyt a3
43. What is the effect of first adding oligomycin and then 2,4-dinitrophenol to respiring mitochondria?
a.
First, electron transport and ATP synthesis speed up, then electron transport and ATP
synthesis stops.
b.
First, ATP synthesis and electron transport stop, then electron transport speeds up with no
ATP synthesis.
c.
First, electron transport speeds up while ATP synthesis stops, then electron transport and
ATP synthesis stops.
d.
First, electron transport stops while ATP synthesis continues, then electron transport and
ATP synthesis stops.
e.
Nothing, the uncoupler and inhibitor cancel each other out.
44. All are properties of uncouplers EXCEPT:
a.
They dissipate the proton gradient.
b.
ATP/ADP ratio increases.
c.
Electron transport continues.
d.
They were briefly used as weight-loss drugs.
e.
Heat is produced.
45. ____ creates a passive proton channel through which protons flow from the cytosol to the
mitochondrial matrix in ____.
a.
Oligomycin; microorganisms
b.
Thermogenin (UCP1); brown adipose tissue
c.
Demerol; nerve tissue
d.
Obesin; adipocytes
e.
none of the above
46. P/O ratio is defined as:
a.
Pi uptake per oxygen atom by mitochondria.
b.
molecules of phosphate released from ATP per oxygen utilized by muscle tissue.
c.
ratio of atoms of phosphorous to oxygen in phosphate (Pi).
d.
molecules of ATP formed per two electrons flowing through electron transport chain.
e.
none of the above.
47. What percentage of the proton gradient energy to synthesize and transport ATP to the cytosol is
involved in the ATP-ADP transport?
a.
10%
b.
15%
c.
25%
d.
50%
e.
none of the above
48. All of the following are part of apoptosis EXCEPT:
a.
cytochrome c is released.
b.
caspases are activated.
c.
a series of proteolytic reactions.
d.
the mitochondrial outer membrane protein-permeable pores close.
e.
mitochondrial membrane permeabilization (MMP).
49. Which of the following molecules is LEAST LIKELY to be transported across the inner mitochondrial
membrane?
a.
citrate
b.
NADH
c.
pyruvate
d.
phosphate
e.
malate
50. A characteristic of the glycerophosphate shuttle is:
a.
It shuttles NADH across the mitochondrial membrane to yield 2.5 ATP/ADH.
b.
It shuttles “NADH electron equivalents” across the mitochondrial membrane to yield 1.5
ATP/NADH.
c.
It only operates efficiently when the [NADH] in the cytoplasm is higher than in the
matrix.
d.
Malate is a key component in the shuttle process.
e.
Aspartate is a key component in the shuttle process.
51. The reaction, dihydroxyacetone phosphate (DHAP) + NADH → NAD+ + glycerol-3-phosphate, is
catalyzed by:
a.
triose phosphate isomerase.
b.
glycerol kinase.
c.
DHAP dehydrogenase.
d.
glycerol-3-phosphate dehydrogenase.
e.
glycerol-3-phosphate reductase.
52. All are properties of glycerol-3-phosphate dehydrogenases EXCEPT:
a.
one is located in the cytosol.
b.
works to carry electrons into mitochondria.
c.
one is located in the inner mitochondrial membrane.
d.
mitochondrial enzyme has bound coenzyme Q.
e.
FAD-dependent mitochondrial enzyme.
53. All are correct about the glycerophosphate shuttle EXCEPT:
a.
there are two distinct forms of glycerol-3-phosphate dehydrogenase in cells with this
shuttle.
b.
it results in the net transfer of electrons to the electron transport chain from NADH in the
cytosol.
c.
glycerol-3-phosphate is translocated across the inner mitochondrial membrane into the
matrix.
d.
electrons derived from this shuttle enter the electron transport chain at UQ.
e.
one form of glycerol-3-phosphate dehydrogenase is a flavoprotein.
54. The malate-aspartate shuttle transfers ____ from cytosol to matrix while _____ moves from matrix to
cytosol
a.
malate; glutamate
b.
-ketoglutarate; aspartate
c.
malate; -ketoglutarate
d.
aspartate; malate
e.
glutamate; malate
55. All are characteristics of the malate-aspartate shuttle EXCEPT:
a.
OAA translocates inner mitochondrial membrane.
b.
electrons of cytosolic NADH are translocated to mitochondrial NADH.
c.
two malate dehydrogenase enzymes.
d.
reactions are reversible.
e.
all are true.
56. Bacteria and other prokaryotic cells have the capacity to get more ATP/glucose oxidized than
eukaryotic cells because ____, so they are more efficient.
a.
they are simpler and have less going on
b.
they don’t have to use shuttles to reoxidize reduced nucleotides
c.
they do not have to translocate ATP-ADP across the mitochondrial membranes
d.
they use an electron transport chain that translocates more protons
e.
none of the above
57. Which of the following correctly and completely describes electron movement in electron transport?
a.
NADH → complex I → complex III → coenzyme Q → Complex IV → O2
b.
[FADH2] → complex II → cytochrome c → complex III → coenzyme Q → Complex IV
→ O2
c.
NADH → complex I → coenzyme Q → complex III → cytochrome c → Complex IV → O2
d.
[FADH2] → complex I → coenzyme Q →complex III → Complex IV → O2
e.
none of the above
58. Which of the following statements about mitochondrial transport systems is correct?
a.
malate-aspartate shuttle: converts cytosolic NADH to mitochondrial FADH2
b.
ATP-ADP translocase: transfers ATP and a proton from matrix to cytosol while
transferring ADP from cytosol to matrix
c.
glycerophosphate shuttle: converts cytosolic FADH2 to mitochondrial NADH
d.
the malate-aspartate shuttle is irreversible while the glycerophosphate shuttle is reversible
e.
none of the above are correct
59. Which of the following is true regarding proton movement in the mitochondria?
a.
complex III pumps 2 protons across the inner membrane
b.
protons move from the matrix to the inner membrane space via the a and c subunits of
ATP synthase to produce ATP
c.
2,4-dinitrophenol moves protons from the inner membrane space to the matrix without
ATP synthesis
d.
the matrix becomes acidic due to the proton movement coupled to electron transport
e.
none of the above
60. If an ATP synthase contains 10 c subunits, 3 subunits and 3 subunits, how many protons must pass
through this complex for every ATP molecule synthesized (assuming that all of the protons are used
for ATP synthesis)?
a.
0.3
b.
3
c.
3.3
d.
10
e.
cannot be determined
61. A molecule such as 2,4-dinitrophenol works to uncouple the proton gradient. Which of the following
is true about 2,4-DNP?
a.
2,4-DNP is protonated in the matrix and deprotonated in the intermembrane space.
b.
The presence of an uncoupler results in an increase in the activity of the TCA cycle and
electron transport
c.
2,4-DNP is a very ineffective uncoupler because its hydrophobic structure prevents it from
effectively crossing lipid bilayer membranes.
d.
2,4-DNP has been used as a very effective diet aid for the past 70 years
e.
none of the above are correct
62. If an ATP synthase contains 12 c subunits, 3 subunits and 3 subunits, how many protons must pass
through this complex for every ATP molecule synthesized and transported to the cytosol, assuming
that each ATP synthesized requires one proton for transport to the cytosol.
a.
3
b.
4
c.
5
d.
12
e.
13