Biochem Chapter 20

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Chapter 20

Question Answer
ATP made in glycolysis and the TCA cycle is the result of _________ phosphorylation, and ADH-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
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
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
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.
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
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.
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
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.
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
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.
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.
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.
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.
Which complex reduces molecular oxygen?
a. complex I
b. complex II
c. complex III
d. UQH/UQH2 pool
e. complex IV
Complex I contains all of these components EXCEPT:
a. [FMN].
b. 2Fe-2S clusters.
c. 4Fe-4S clusters.
d. cytochrome c.
e. "proton pump."
Which of the following is a two-electron donor?
a. FAD
b. Fe-S
d. NAD+
e. cyt c
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.
In the first phase of the Q cycle, UQH2 transfers one electron to __________ and then to ___________, releasing _______ H+ to the intermembrane space leaving _________ that transfers a second electron to ________.
a. cyt c; Rieske protein; one; UQ; cyt bH
b. cyt bL; cyt bH; two; UQ; cyt c1
c. cyt c1; Rieske protein; one; UQ.-; cyt bH
d. Rieske protein; cyt c1; two; UQ.-; cyt bL
e. Rieske protein; cyt bL; one; UQ.-; cyt c1
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.
Which of the following is/are mobile electron carrier(s)?

B. Cyt c
C. Complex III
a. A only
b. B only
c. C only
d. B & C
e. A & B
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
All are single-electron carriers EXCEPT:
a. UQH2.
b. Cyt bL.
c. Cyt bH.
d. Rieske protein Fe-S clusters.
e. Cyt c1.
The final electron acceptor in the electron transport chain is:
a. molecular oxygen.
b. H2O.
c. cytochrome c.
d. UQ.
e. NAD+.
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.
All are components of cytochrome c oxidase (complex IV) EXCEPT:
a. CuA.
b. CuB.
c. Cyt c1.
d. Cyt a3.
e. Cyt a.
The complete reduction of one molecule of oxygen gas requires how many electrons?
a. two
b. three
c. four
d. eight
e. six
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.
What molecule is the electron donor to complex III?
a. cytochrome c
b. UQH2
d. H2O
e. FADH2
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.
Which of the following complex(es) translocate protons in the inner mitochondrial membrane?

1. Complex I
2. Complex II
3. Complex III
4. Complex IV

a. 1, 3 & 4
b. 1 & 2
c. 1, 2 & 4
d. 4 only
e. all of the above
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.
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. β-subunits have catalytic sites for ATP synthesis.
d. α- and β-subunits are homologous.
e. all are true.
In ATP synthase, it is proposed that ___-subunits form a rotor that turns with respect to ____-subunits and the _____-subunit is anchored to the rotor.
a. α; β; γ
b. c; β; α
c. c; γ; β
d. c; α; γ
e. b; α; γ
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.
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 β-subunits releasing ATP.
e. (αβ)3 complex rotates relative to a fixed β-subunit.
The hypothesis for proton driven ATP synthesis depends on ________ neutralization of the negative charge on c-subunit ______ residues as the rotor turns causing the ____-subunit to turn relative to the three ____-subunit ______ binding sites of F1, changing the conformation of each in sequence.
a. electron; Ser; c; γ; nucleotide
b. proton; Ser; b; β; proton
c. proton; Asp; β; γ; nucleotide
d. electron; Arg; c; γ; proton
e. proton; Asp; γ; β; nucleotide
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
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.
Which of the following is an inhibitor of Complex IV?
a. rotenone
b. oligomycin
c. antimycin
d. cyanide
e. all of the above
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
What is the effect of adding oligomycin and then 2,4-dinitrophenol to respiring mitochondria?
a. Electron transport speeds up and ATP synthesis stops.
b. Electron transport continues and ATP synthesis continues.
c. Electron transport stops and ATP synthesis stops.
d. Nothing, the uncoupler and inhibitor cancel each other out.
e. Electron transport stops and ATP synthesis continues.
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.
_____________ 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
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.
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
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).
Which of the following molecules is LEAST LIKELY to be transported across the inner mitochondrial membrane?
a. citrate
c. pyruvate
d. phosphate
e. malate
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.
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.
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.
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.
The appropriate sequence for the malate-aspartate shuttle is:
A. OAA transaminated to aspartate
B. OAA reduced to malate
C. Malate oxidized to OAA
D. Malate translocated to matrix
E. Aspartate translocated to cytosol
F. Aspartate transaminated to QAA
a. A, F, C, B, D, E
b. B, A, D, F, C, E
c. B, E, D, C, F, A
d. C, D, F, E, A, B
e. B, D, C, A, E, F
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.
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