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Chemistry
Q:
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
Q:
Which of the following is an inhibitor of Complex IV?
a. rotenone
b. oligomycin
c. antimycin
d. cyanide
e. all of the above
Q:
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.
Q:
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
Q:
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.
Q:
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.
Q:
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.
Q:
In ATP synthase, the ____ subunit is the site of ATP synthesis while the ____ subunit forms the proton channel through the inner mitochondrial membrane.
Q:
All are true for F1unit of ATP synthase EXCEPT:a. consists of five different kinds of subunits.b. catalyzes ATP hydrolysis as well as ATP synthesis.e. all are true.
Q:
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.
Q:
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.
Q:
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. Feï€S is a component.
Q:
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
Q:
All of the following transfer electrons to the UQ/UQH2pool EXCEPT:
a. fatty acyl-CoA dehydrogenase.
b. sn-glycerolphosphate dehydrogenase.
c. Complex I.
d. Complex II.
e. Complex IV.
Q:
What molecule is the electron donor to complex III?
a. cytochrome c
b. UQH2
c. NADH
d. H2O
e. FADH2
Q:
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.
Q:
The complete reduction of one molecule of oxygen gas requires how many electrons?
a. two
b. three
c. four
d. eight
e. six
Q:
All are components of cytochrome coxidase (complex IV) EXCEPT:
a. CuA.
b. CuB.
c. Cyt c1.
d. Cyt a3.
e. Cyt a.
Q:
All are characteristics of cyt cEXCEPT:
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.
Q:
The final electron acceptor in the electron transport chain is:
a. molecular oxygen.
b. H2O.
c. cytochrome c.
d. UQ.
e. NAD+.
Q:
All are single-electron carriers EXCEPT:
a. UQH2.
b. Cyt bL.
c. Cyt bH.
d. Rieske protein Feï€S clusters.
e. Cyt c1.
Q:
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
Q:
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
Q:
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.
Q:
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 (UQï‚·-) 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
Q:
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.
Q:
Which of the following is a two-electron donor?a. FADb. Fe-Sc. NADHd. NAD+e. cyt c
Q:
Complex I contains all of these components EXCEPT:a. [FMN].b. 2Fe-2S clusters.c. 4Fe-4S clusters.d. cytochrome c.e. "proton pump."
Q:
Which complex reduces molecular oxygen?
a. complex I
b. complex II
c. complex III
d. UQH/UQH2 pool
e. complex IV
Q:
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.
Q:
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.
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.
Q:
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.
Q:
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
Q:
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.
Q:
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
Q:
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.
Q:
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.
Q:
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.
Q:
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
Q:
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
Q:
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
Q:
Which of the following enzymes catalyzes an endergonic step of the citric acid cycle?a. citrate synthaseb. malate dehydrogenasec. -ketoglutarate dehydrogenased. isocitrate dehydrogenasee. none of the above
Q:
Which of the following statements regarding the glyoxylate cycle is true?
a. the process takes place in the mitochondria
b. two molecules of acetyl CoA can be converted to one molecule of oxaloacetate
c. isocitrate dehydrogenase and malate dehydrogenase are not used
d. the primary role is to allow for the synthesis of amino acids from fatty acids
e. none of the above
Q:
Which of the following is correctly paired with its inhibitor?
a. pyruvate dehydrogenase: phosphorylation
b. isocitrate dehydrogenase: AMP
c. ï¡-ketoglutarate dehydrogenase: NAD+
d. citrate synthase: acetyl CoA
e. none of the above are correct
Q:
Which of the following coenzymes is NOT used by pyruvate dehydrogenase?
a. NAD+
b. FAD
c. thiamine pyrophosphate
d. tetrahydrofolate
e. lipoic acid
Q:
The glyoxylate cycle reaction that is catalyzed by malate synthase involves the condensation of acetyl CoA with _____. The mechanism is most similar to the TCA cycle enzyme _____.
a. succinate; fumarase
b. isocitrate; succinyl-CoA synthetase
c. glyoxylate; citrate synthase
d. oxaloacetate; aconitase
e. acetyl CoA; isocitrate lyase
Q:
The isocitrate lyase catalyzed reaction cleaves isocitrate into:
a. glyoxylate and fumarate.
b. succinate and acetyl-CoA.
c. malate and acetyl-CoA.
d. succinate and glyoxylate.
e. glyoxylate and acetyl-CoA.
Q:
All are true statements for the glyoxylate pathway EXCEPT:
a. the glyoxylate pathway enzymes are found in the glyoxysomes.
b. although glyoxysomes are found in germinating seeds, they disappear after a plant begins photosynthesis.
c. glyoxysomes contain all of the enzymes for the glyoxylate cycle.
d. bypasses the oxidative-decarboxylation steps of the TCA cycle.
e. isocitrate is routed through isocitrate lyase and malate synthase.
Q:
An essential feature of the glyoxylate cycle, which is not associated with the TCA cycle is:
a. it utilizes condensation of acetyl-CoA with glyoxylate
b. each complete cycle produces a net gain of two 4-carbon molecules
c. it occurs in chloroplasts and the mitochondria of plant seeds
d. mammals use the glyoxylate cycle for gluconeogenesis
e. it is a reductive pathway that utilizes NADPH as an electron source
Q:
All of the following are inhibitors of citrate synthase EXCEPT:
a. acetyl-CoA
b. NADH
c. succinyl-CoA
d. ATP
e. all are inhibitors
Q:
Inhibition of the citric acid cycle at isocitrate dehydrogenase increases the levels of citrate and isocitrate that may increase the production of:
a. amino acids.
b. pyruvate and oxaloacetate.
c. glyoxylate and cytosolic acetyl-CoA.
d. succinate and fumarate.
e. lactate and alanine.
Q:
In mammalian tissues, isocitrate dehydrogenase is allosterically stimulated by:
a. high NAD+/NADH and high ADP/ATP ratios.
b. low ADP/ATP and low NAD+/NADH ratios.
c. high NAD+/NADH and low ADP/ATP ratios.
d. low NAD+/NADH and high ADP/ATP ratios.
e. none of the above.
Q:
Mammalian pyruvate dehydrogenase is regulated by phosphorylation using the enzyme ____ which is allosterically activated by high levels of ____ and ____.
a. pyruvate kinase; ATP; acetyl-CoA
b. pyruvate kinase; NADH; NADPH
c. pyruvate carboxylase; acetyl-CoA; ATP
d. pyruvate dehydrogenase kinase; NADH; acetyl-CoA
e. pyruvate dehydrogenase kinase; ADP; NAD+
Q:
It is crucial that regulation occur at pyruvate dehydrogenase because:
a. pyruvate kinase is reversible.
b. lactate dehydrogenase is the only other enzyme to use pyruvate.
c. the product acetyl-CoA is committed to oxidation in the citric acid cycle or fatty acid biosynthesis.
d. alanine aminotransferase would use the pyruvate.
e. all of the above.
Q:
All are principal allosteric regulatory "signals" controlling the TCA cycle activity EXCEPT:
a. acetyl-CoA.
b. NADH.
c. NAD+.
d. ATP.
e. all are true.
Q:
The three reactions of the citric acid cycle with large negative ï„G values include:
A. citrate synthase.
B. aconitase.
C. isocitrate dehydrogenase.
D. ï¡-ketoglutarate dehydrogenase.
E. succinyl-CoA synthetase.
F. succinyl-CoA dehydrogenase.
G. fumarase.
H. malate dehydrogenase.
a. A, B, C
b. A, C, D
c. C, E, F
d. B, C, E
e. A, C, H
Q:
The reaction CO2+ PEP + GDP OAA + GTP is catalyzed by:
a. PEP carboxylase.
b. PEP carboxykinase.
c. malic enzyme.
d. pyruvate carboxylase.
e. None are true.
Q:
All are true for pyruvate carboxylase EXCEPT:
a. an anaplerotic reaction.
b. in mitochondria of plants, but not animals.
c. is tetrameric.
d. contains covalently bound biotin.
e. absolute allosteric requirement for acetyl-CoA.
Q:
When acetyl-CoA levels exceed the ____ supply, allosteric activation of ____ by ____ raises the oxaloacetate (OAA) levels for condensation with acetyl-CoA to form ____.
a. citrate; citrate synthase; acetyl-CoA; citrate
b. malate; malate dehydrogenase; ATP; citrate
c. OAA; citrate synthase; acetyl-CoA; isocitrate
d. OAA; pyruvate carboxylase; acetyl-CoA; citrate
e. Acetyl-CoA; pyruvate carboxylase; citrate; acetyl-CoA
Q:
The anaplerotic reactions associated with the TCA cycle are a result of the:
a. use of many of the TCA cycle intermediates in biosynthesis.
b. oxidative nature of the TCA cycle.
c. decarboxylation reactions.
d. production of GTP and reduced coenzymes.
e. irreversible nature of some of the TCA cycle reactions.
Q:
Which of the following represents a reaction that could be used to refill the CAC?:a. OAA -> PEPb. citrate -> OAA + acetyl-CoAc. Asp -> -ketoglutarated. pyruvate -> OAAe. none of the above
Q:
In the TCA cycle, ____ oxidation(s) use(s) NAD+as the oxidizing agent while ____ oxidation(s) use(s) FAD as the oxidizing agent.
a. 0; 4
b. 1; 3
c. 2; 2
d. 3; 1
e. 4; 0
Q:
The oxidation of malate to oxaloacetate is not thermodynamically favored under standard conditions. It occurs because:
a. it involves substrate-level phosphorylation.
b. it is coupled with a strong reduction.
c. it is coupled with ATP hydrolysis.
d. oxaloacetate is used in the next reaction, which has a negative ï„G.
e. the previous reaction has a large negative ï„G.
Q:
Characteristics of the oxidation of malate to oxaloacetate (OAA) include all EXCEPT:
a. catalyzed by malate dehydrogenase.
b. uses NAD+ as an electron acceptor.
c. is very exergonic.
d. results in higher levels of malate than oxaloacetate.
e. is structurally and functionally similar to lactate dehydrogenase.
Q:
Fumarase catalyzes a reaction for which each of the following is true EXCEPT:
a. fumarate is hydrated
b. the reaction is stereospecific for a trans product
c. the reaction involved is similar to that carried out by aconitase
d. L-malate is the produced
e. all are true
Q:
The correct sequence of electron transport in the succinate dehydrogenase reaction mechanism is:
A. Coenzyme Q (UQ).
B. [FAD].
C. iron-sulfur clusters.
D. electron transport chain.
a. A, B, C, D
b. B, C, D, A
c. B, C, A, D
d. C, B, D, A
e. C, D, A, B
Q:
The succinate dehydrogenase catalyzed reaction involves dehydrogenation ____ to a carbonyl group and is ____ to yield a ____ double bond.
Q:
The succinate dehydrogenase mechanism involves the ____ of succinate, which is exergonic and can be used to provide for the ____.
a. oxidation; reduction of NAD+
b. reduction; oxidation of NAD+
c. oxidation; reduction of [FAD]
d. reduction; oxidation of [FAD]
e. none are true
Q:
Characteristics of succinate dehydrogenase include all EXCEPT:
a. it is also known as succinate-Coenzyme Q reductase.
b. it has covalently bound FAD.
c. it is a membrane-bound enzyme.
d. it removes hydrogens from C-O bonds.
e. it carries out either 1-electron or 2-electron transfers to/from FAD.
Q:
The correct sequence of steps between succinyl-CoA and ATP in mammals to "preserve" the energy of the thioester bond are:
A. succinyl-phosphate.
B. phosphohistidine.
C. GTP.
D. Acetyl-CoA.
a. A, B, C
b. B, C, A
c. A, C, D
d. C, B, A
e. D, A, B
Q:
All are characteristics of succinyl-CoA synthetase EXCEPT:
a. succinyl-CoA can be used to drive phosphorylation of GDP or ADP.
b. the enzyme is named for the reverse reaction.
c. it provides an example of substrate-level phosphorylation.
d. succinyl-phosphate is an intermediate in the reaction catalyzed by succinyl-CoA synthetase.
e. all of the above are true.
Q:
The only reaction of the citric acid cycle that provides substrate-level phosphorylation is catalyzed by:
a. malate dehydrogenase.
b. citrate synthase.
c. isocitrate dehydrogenase.
d. succinyl-CoA synthetase.
e. nucleotide triphosphate kinase.
Q:
The coenzymes listed below are associated with -ketoglutarate dehydrogenase complex EXCEPT:a. [FAD].b. TPP.c. lipoamide.d. NAD+.e. biotin.
Q:
-Ketoglutarate dehydrogenase is a multi-enzyme complex analogous to:a. pyruvate kinase.b. glyceraldehyde-3-phosphate dehydrogenase.c. isocitrate dehydrogenase.d. pyruvate dehydrogenase.e. lactate dehydrogenase.
Q:
Isocitrate dehydrogenase has all of the characteristics EXCEPT:
a. ADP raises the Km for isocitrate by a factor of 10.
b. virtually inactive in the absence of ADP.
c. sufficiently exergonic to pull the aconitase reaction forward.
d. allosterically inhibited by NADH and ATP.
e. an oxidative-decarboxylation reaction.
Q:
Allosteric inhibitors of isocitrate dehydrogenase include ____ and ____, whereas ____ acts as an allosteric activator, ____ the Kmfor isocitrate.
a. ATP; NADH; ADP; lowering
b. ATP; ADP; AMP; lowering
c. NADH; NADPH; AMP; increasing
d. NADH; ATP; ADP; increasing
e. NADH; ATP; AMP; lowering
Q:
The two step reaction catalyzed by isocitrate dehydrogenase involves:A. -decarboxylation expelling the -keto carboxyl as CO2.B. oxidation of the C-2 alcohol of isocitrate to form oxalosuccinate.C. oxidation of the C-2 alcohol to form oxaloacetate.D. -elimination expelling the central carboxyl group as CO2.a. A and Bb. B and Cc. C and Dd. A and Ce. B and D
Q:
Which enzymes of the TCA cycle catalyze oxidative decarboxylation reactions?a. malate dehydrogenase and citrate synthaseb. fumarase and succinate dehydrogenasec. -ketoglutarate dehydrogenase and succinate dehydrogenased. isocitrate dehydrogenase and -ketoglutarate dehydrogenasee. aconitase and succinate dehydrogenase
Q:
Fluoroacetate is a potent inhibitor of the TCA cycle. Which step of the TCA cycle is inhibited as a result of fluoroacetate entering the TCA cycle?a. citrate synthaseb. aconitasec. isocitrate dehydrogenased. -ketoglutarate dehydrogenasee. succinyl-CoA synthetase