Biochemistry Test 6

187 Questions

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  • 1. 
     In the TCA cycle, carbon enters the cycle as ____ and exits as ____ with metabolic energy captured as ____, ____ and ____. 
    • A. 

      Acetyl-CoA; CO2; ATP; NADH; [FADH2]

    • B. 

      Malonyl-CoA; water; NADH; [FADH2]; ATP

    • C. 

       succinyl-CoA; CO2; ATP; NADH; NADPH

    • D. 

       acetyl-CoA; CO2; NADH; ATP; NADPH

    • E. 

      Malonate; water; NADH; ATP; NADPH


  • 2. 
     In eukaryotic cells, glycolysis occurs in the ____, and the TCA cycle reactions take place in ____. 
    • A. 

      Mitochondria; mitochondria

    • B. 

      Cytoplasm; mitochondria

    • C. 

      Cytoplasm; cytoplasm


    • D. 

      Mitochondria; ribosomes


    • E. 

      Cytoplasm; ribosomes

  • 3. 
    The ____ of pyruvate to acetyl-CoA is catalyzed by ____. 
    • A. 

      Dehydration; pyruvate dehydration complex

    • B. 

      Decarboxylation; pyruvate dehydrogenase complex

    • C. 

      Decarboxylation; pyruvate decarboxylase

    • D. 

      Transacylation; pyruvate transacylase


    • E. 

       none of the above.

  • 4. 
    • A. 

      It uses thiamin pyrophosphate as a catalytic coenzyme.

    • B. 

      It oxidatively decarboxylates pyruvate.

    • C. 

      It binds NAD+ in its active site.

    • D. 

      It transfers an acetyl group to lipoamide of ETA.

    • E. 

      It forms a hydroxyethyl-TPP intermediate.

  • 5. 
    • A. 

       it is the link between glycolysis and the TCA cycle

    • B. 

      The activity of the complex is regulated by the phosphorylation of EPDH.

    • C. 

      NAD+ is the direct oxidant of reduced lipoamide.

    • D. 

      An FAD is covalently linked to the EDLD, the lipoamide dehydrogenase component.

    • E. 

      Although EPDH is called "pyruvate dehydrogenase" it is not a dehydrogenase.

  • 6. 
    Order the coenzymes according to their involvement in the pyruvate dehydrogenase complex.
    • A. 

      A, B, C, D, E 

    • B. 

       C, B, A, E, D

    • C. 

      C, D, B, E, A

    • D. 

      B, D, E, A, C

    • E. 

      C, E, D, B, A

  • 7. 
    • A. 

      Citrate synthase is allosterically activated by ATP.

    • B. 

      The complete chemical equation is: Oxaloacetate + acetyl-CoA + H2O -> citrate + CoA

    • C. 

      Citryl-CoA is formed as an intermediate.

    • D. 

      The mechanism involves attack of the carbanion of acetyl-CoA on the carbonyl carbon of oxaloacetate.

    • E. 

      The enzyme uses general base catalysis to generate the reactive species.

  • 8. 
    Citrate synthase has a ____ DG¢ and is essentially ____ due to the ____ of the CoA thioester. 
    • A. 

      Large positive; reversible; oxidation

    • B. 

      Nearly zero; reversible; reduction

    • C. 

      Nearly zero; irreversible; reduction

    • D. 

       large negative; irreversible; hydrolysis

    • E. 

      Large negative; reversible; hydrolysis

  • 9. 
    Citrate synthase is a ____ with binding of ____ inducing a conformational change ____ the binding of acetyl-CoA, and ____ is an allosteric inhibitor. 
    • A. 

      Dimer; OAA; increasing; NADH

    • B. 

      Dimer; OAA; decreasing; NADH

    • C. 

      Tetramer; OAA; decreasing; NAD+

    • D. 

      Monomer; pyruvate; decreasing; ATP

    • E. 

      Monomer; pyruvate; increasing; ATP

  • 10. 
     Which is NOT true of citrate synthase? 
    • A. 

      It catalyzes the first reaction in the TCA cycle

    • B. 

      It is not regulated

    • C. 

      OAA and acetyl-CoA bind to the active sites

    • D. 

      The citrate synthase reaction liberates a relatively large amount of energy

    • E. 

      All of the above are true

  • 11. 
    Citrate must be isomerized to isocitrate because the ____ group of citrate is not oxidizable, but the ____ group of isocitrate can be oxidized. 
    • A. 

      Ketone; primary alcohol

    • B. 

      Tertiary alcohol; secondary alcohol

    • C. 

      Ketone; secondary alcohol

    • D. 

      Aldehyde; primary alcohol

    • E. 

      Secondary alcohol; ketone

  • 12. 
    ____ catalyzes citrate isomerization to isocitrate by abstracting ____ from citrate to yield the enzyme-bound intermediate ____, followed by ____ to produce isocitrate. 
    • A. 

      Citrate isomerase; CO2; trans-aconitate; carboxylation

    • B. 

      Citrate isomerase; water; trans-aconitate; rehydration

    • C. 

      Aconitase; water; cis-aconitate; rehydration

    • D. 

      Aconitase; CO2; cis-aconitate; carboxylation

    • E. 

      None are true

  • 13. 
    All are true for aconitase EXCEPT: 
    • A. 

      Iron atom acts as a Lewis acid.

    • B. 

      Equilibrium favors citrate.

    • C. 

      Contains an iron-sulfur cluster.

    • D. 

      One Fe3+ coordinates with C-3 carbonyl and hydroxyl group of citrate.

    • E. 

      All are true.

  • 14. 
    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 synthase

    • B. 

      Aconitase

    • C. 

      Isocitrate dehydrogenase

    • D. 

      A-ketoglutarate dehydrogenase

    • E. 

      Succinyl-CoA synthetase

  • 15. 
    Which enzymes of the TCA cycle catalyze oxidative decarboxylation reactions? 
    • A. 

       malate dehydrogenase and citrate synthase


    • B. 

      Fumarase and succinate dehydrogenase

    • C. 

      A-ketoglutarate dehydrogenase and succinate dehydrogenase


    • D. 

      Isocitrate dehydrogenase and a-ketoglutarate dehydrogenase


    • E. 

       aconitase and succinate dehydrogenase

  • 16. 
    The two step reaction catalyzed by isocitrate dehydrogenase involves:
    • A. 

      A and B

    • B. 

      B and C

    • C. 

      C and D

    • D. 

      A and C

    • E. 

      B and D

  • 17. 
    Allosteric inhibitors of isocitrate dehydrogenase include ____ and ____, whereas ____ acts as an allosteric activator, ____ the Km for 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

  • 18. 
    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.

  • 19. 
    A-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.

  • 20. 
    The coenzymes listed below are associated with a-ketoglutarate dehydrogenase complex EXCEPT: 
    • A. 

       [FAD].

    • B. 

      TPP.

    • C. 

      Lipoamide.

    • D. 

      NAD+.

    • E. 

      Biotin.

  • 21. 
    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.

  • 22. 
    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.

  • 23. 
    The correct sequence of steps between succinyl-CoA and ATP in mammals to "preserve" the energy of the thioester bond are:
    • A. 

      A, B, C

    • B. 

      B, C, A

    • C. 

      A, C, D

    • D. 

      C, B, A

    • E. 

      D, A, B

  • 24. 
    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.

  • 25. 
    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

  • 26. 
    The succinate dehydrogenase catalyzed reaction involves dehydrogenation ____ to a carbonyl group and is ____ to yield a ____ double bond. 
    • A. 

      B,b; electrophilic; trans

    • B. 

      A,b; stereospecific; trans

    • C. 

      A,b; electrophilic; cis

    • D. 

      B,g; stereospecific; cis

    • E. 

      None are true

  • 27. 
    The correct sequence of electron transport in the succinate dehydrogenase reaction mechanism is:
    • 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

  • 28. 
    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

  • 29. 
    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. 

      Results in higher levels of malate than oxaloacetate.

    • D. 

      Is very exergonic.

    • E. 

      Is structurally and functionally similar to lactate dehydrogenase.

  • 30. 
    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 DG.

    • E. 

      The previous reaction has a large negative DG.

  • 31. 
    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

  • 32. 
     Which of the following represents a reaction that could be used to refill the CAC?: 
    • A. 

      OAA -> PEP

    • B. 

      Citrate -> OAA + acetyl-CoA

    • C. 

      Asp -> a-ketoglutarate

    • D. 

      Pyruvate -> OAA

    • E. 

      None of the above

  • 33. 
    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.

  • 34. 
    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

  • 35. 
    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.

  • 36. 
    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.

  • 37. 
    The three reactions of the citric acid cycle with large negative DG values include:
    • A. 

      A, B, C

    • B. 

      A, C, D

    • C. 

      C, E, F


    • D. 

      B, C, E

    • E. 

      A, C, H

  • 38. 
    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.

  • 39. 
    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.

  • 40. 
    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+

  • 41. 
     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.

  • 42. 
    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.

  • 43. 
    All of the following are inhibitors of citrate synthase EXCEPT: 
    • A. 

      Acetyl-CoA

    • B. 

      NADH

    • C. 

      Succinyl-CoA

    • D. 

      ATP

    • E. 

      All are inhibitors

  • 44. 
     An essential feature of the glyoxylate cycle, which is not associated with the TCA cycle is: 
    • A. 

      Each complete cycle produces a net gain of two 4-carbon molecules

    • B. 

      It utilizes condensation of acetyl-CoA with glyoxylate

    • 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

  • 45. 
    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.

  • 46. 
    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.

  • 47. 
    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

  • 48. 
     Which of the following coenzymes is NOT used by pyruvate dehydrogenase? 
    • A. 

      NAD+

    • B. 

      FAD

    • C. 

      Thiamine pyrophosphate

    • D. 

      Tetrahydrofolate

    • E. 

      Lipoic acid

  • 49. 
    Which of the following is correctly paired with its inhibitor? 
    • A. 

      Pyruvate dehydrogenase:  phosphorylation

    • B. 

      Isocitrate dehydrogenase:  AMP

    • C. 

      A-ketoglutarate dehydrogenase:  NAD+

    • D. 

      Citrate synthase:  acetyl CoA

    • E. 

       none of the above are correct

  • 50. 
    • A. 

      The process takes place in the mitochondria

    • B. 

      Two molecules of acetyl CoA can be converted to one molecule of oxaloacetate

    • C. 

      Two molecules of acetyl CoA can be converted to one molecule of oxaloacetate

    • D. 

      The primary role is to allow for the synthesis of amino acids from fatty acids

    • E. 

      None of the above

  • 51. 
    Which of the following enzymes catalyzes an endergonic step of the citric acid cycle? 
    • A. 

      Citrate synthase

    • B. 

      Malate dehydrogenase

    • C. 

      A-ketoglutarate dehydrogenase

    • D. 

      Isocitrate dehydrogenase

    • E. 

      None of the above

  • 52. 
    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

  • 53. 
    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

  • 54. 
     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

  • 55. 
    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.

  • 56. 
    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.

  • 57. 
    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.

  • 58. 
    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

  • 59. 
    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.

  • 60. 
    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

  • 61. 
    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.

  • 62. 
    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.

  • 63. 
    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.

  • 64. 
    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.

  • 65. 
    Which complex reduces molecular oxygen? 
    • A. 

      Complex I


    • B. 

      Complex II


    • C. 

      Complex II
I

    • D. 

      UQH/UQH2 pool

    • E. 

      Complex IV

  • 66. 
     Complex I contains all of these components EXCEPT: 
    • A. 

      [FMN].

    • B. 

      2Fe-2S clusters.

    • C. 

      4Fe-4S clusters.

    • D. 

      Cytochrome c.

    • E. 

      "proton pump."

  • 67. 
     Which of the following is a two-electron donor? 
    • A. 

      FAD

    • B. 

      Fe-S

    • C. 

      NADH

    • D. 

      NAD+

    • E. 

      Cyt c

  • 68. 
    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.

  • 69. 
     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

  • 70. 
    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.

  • 71. 
    Which of the following is/are mobile electron carrier(s)?
    • A. 

      A only

    • B. 

      B only

    • C. 

      C only

    • D. 

      B & C

    • E. 

      A & B

  • 72. 
    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

  • 73. 
    All are single-electron carriers EXCEPT: 
    • A. 

      UQH2.

    • B. 

      Cyt bL.

    • C. 

      Cyt bH.

    • D. 

      Rieske protein Fe-S clusters.

    • E. 

      Cyt c1.

  • 74. 
    The final electron acceptor in the electron transport chain is: 
    • A. 

      Molecular oxygen

    • B. 

      H2O.

    • C. 

      Cytochrome c.

    • D. 

      UQ.

    • E. 

      NAD+.

  • 75. 
    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.

  • 76. 
    All are components of cytochrome c oxidase (complex IV) EXCEPT: 
    • A. 

      CuA.

    • B. 

      CuB.

    • C. 

      Cyt c1.

    • D. 

      Cyt a3.

    • E. 

      Cyt a.

  • 77. 
    The complete reduction of one molecule of oxygen gas requires how many electrons? 
    • A. 

      Two

    • B. 

      Three

    • C. 

      Four

    • D. 

      Eight

    • E. 

      Six

  • 78. 
    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.

  • 79. 
    What molecule is the electron donor to complex III? 
    • A. 

      Cytochrome c

    • B. 

      UQH2

    • C. 

      NADH

    • D. 

      H2O

    • E. 

      FADH2

  • 80. 
    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.

  • 81. 
    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

  • 82. 
    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.

  • 83. 
    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.

  • 84. 
    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.

  • 85. 
    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. 

      B-subunits have catalytic sites for ATP synthesis.

    • D. 

      A- and b-subunits are homologous.

    • E. 

      All are true.

  • 86. 
    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; a

    • B. 

      B; a

    • C. 

      B; c

    • D. 

      G; c

    • E. 

      A;  g

  • 87. 
    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.

  • 88. 
    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 b-subunits releasing ATP.

    • E. 

      (ab)3 complex rotates relative to a fixed b-subunit.

  • 89. 
    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;  g

    • B. 

      Ser;  b;  b

    • C. 

      Asp;  b;  g

    • D. 

      Arg;  c;  g

    • E. 

      Asp;  g;  b

  • 90. 
    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

  • 91. 
    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.

  • 92. 
    Which of the following is an inhibitor of Complex IV? 
    • A. 

      Rotenone

    • B. 

      Oligomycin

    • C. 

      Antimycin

    • D. 

      Cyanide

    • E. 

      All of the above

  • 93. 
    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

  • 94. 
    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.

  • 95. 
    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.

  • 96. 
    ____ 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

  • 97. 
    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.

  • 98. 
    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

  • 99. 
     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).

  • 100. 
     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

  • 101. 
    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.

  • 102. 
    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.

  • 103. 
    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.

  • 104. 
    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.

  • 105. 
    The malate-aspartate shuttle transfers ____ from cytosol to matrix while _____ moves from matrix to cytosol 
    • A. 

      Malate;  glutamate

    • B. 

      A-ketoglutarate;  aspartate

    • C. 

      Malate;  a-ketoglutarate

    • D. 

      Aspartate;  malate

    • E. 

      Glutamate;  malate

  • 106. 
    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.

  • 107. 
    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. 

      None of the above

  • 108. 
    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

  • 109. 
    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

  • 110. 
    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

  • 111. 
    If an ATP synthase contains 10 c subunits, 3 a subunits and 3 b 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

  • 112. 
    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

  • 113. 
    If an ATP synthase contains 12 c subunits, 3 a subunits and 3 b 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

  • 114. 
    Which of the following types of chemical reactions does not occur in the TCA cycle?
    • A. 

      Hydrolysis

    • B. 

      Decarboxylation

    • C. 

      Phosphorylation

    • D. 

      Oxidation-reduction

    • E. 

      Dephosphorylation

  • 115. 
    Pyruvate dehydrogenase is activated by:
    • A. 

      A low ratio of NADH/NAD+

    • B. 

      A high ratio of NADH/NAD+

    • C. 

      A high ratio of GTP/GDP

    • D. 

      A low ratio of ATP/ADP

    • E. 

      A high ratio of acetyl CoA/CoA-SH

  • 116. 
    Fluroacetate inhibits the citric acid cycle. Although it does not inhibit citrate synthase, the product inhibits:
    • A. 

      Aconitase

    • B. 

      Isocitrate dehydrogenase

    • C. 

      A-ketoglutarate dehydrogenase

    • D. 

      Succinate dehydrogenase

    • E. 

      Pyruvate dehydrogenase

  • 117. 
    Which of the following enzymes utilizes biotin?
    • A. 

      Pyruvate dehydrogenase

    • B. 

      Pyruvate carboxylase

    • C. 

      Isocitrate dehydrogenase

    • D. 

      A-ketoglutarate dehydrogenase

    • E. 

      Citrate synthase

  • 118. 
    Which of the following citric acid cycle intermediates are replenished through anapleurotic reactions?
    • A. 

      Citrate

    • B. 

      Isocitrate

    • C. 

      Succinate

    • D. 

      Oxaloacetate

    • E. 

      Malate

  • 119. 
    If C(4) of oxaloacetate is radiolabelled, at what reaction of the TCA cycle will it be released as carbon dioxide?
    • A. 

      Isocitrate dehydrogenase

    • B. 

      A-ketoglutarate dehydrogenase

    • C. 

      Pyruvate dehydrogenase

    • D. 

      C(4) of oxaloavetate will never be released as carbon dioxide

  • 120. 
    Which of the following molecules is capable  of inhibiting pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase and a-ketoglutarate dehydrogenase
    • A. 

      Succintl CoA

    • B. 

      Acetyl CoA

    • C. 

      ATP

    • D. 

      NAD+

    • E. 

      NADH

  • 121. 
    One turn of the citric acid cycle alone results in how many ATP?
    • A. 

      1

    • B. 

      3

    • C. 

      4

    • D. 

      12

    • E. 

      34

  • 122. 
    Starting with one glucose molecule in glycolysis and proceeding though the citric acid cycle, how many molecules of carbon dioxide are produced?
    • A. 

      2

    • B. 

      3

    • C. 

      4

    • D. 

      6

    • E. 

      9

  • 123. 
    What do the enzyme citrate synthase, isocitrate dehydrogenase and ketoglutarate dehydrogenase have in common?
    • A. 

      All are enzymes that release carbon dioxide

    • B. 

      All are enzymes that utilize NAD+

    • C. 

      All are enzymes that catalyze reduction reactions

    • D. 

      All are enzymes with large negative free energies

    • E. 

      All are enzymes that operate close to equilibrium

  • 124. 
    Which of the following enzymes demonstrate substrate level phosphorylation?
    • A. 

      Isocitrate dehydrogenase

    • B. 

      Ketoglutarate dehydrogenase

    • C. 

      Succinyl CoA synthetase

    • D. 

      Succinate dehydrogenase

    • E. 

      Malate dehydrogenase

  • 125. 
    Which of the following events does not occur in the citric acid cycle
    • A. 

      A tertiary alcohol is isomerized to a secondary alcohol

    • B. 

      A trans-addition of H+ and OH- across a double bond

    • C. 

      Oxidation of an alkane to an alkene

    • D. 

      A-cleave of a a-hydroxy ketone

    • E. 

      A carbon-carbon condensation between a ketone and an ester

  • 126. 
    Succinate dehydrogenase reduces FAD+ instead of NAD+ because:
    • A. 

      It has a steric preference for FAD over NAD.

    • B. 

      The reaction does not release enough free energy to reduce NAD+.

    • C. 

      Iron sulfur clusters can only receive electrons from flavin co-enzymes.

    • D. 

      FADH produces more ATP in the electron transport chain than NADH.

    • E. 

      This enzyme does not release any carbon dioxide.

  • 127. 
    While the TCA cycle is focused on energy production, the glyoxylate cycle is focused primarily on:
    • A. 

      Conserving carbon units and other intermediates for carbohydrate synthesis

    • B. 

      Utilizing oxidation reactions

    • C. 

      Carbon dioxide production

    • D. 

      NADH

    • E. 

      ATP production

  • 128. 
    Which of the following substances is dehydrogenated to an a-keto acid in the tricarboxylic acid?
    • A. 

      Citrate

    • B. 

      Glyceraldehyde-3-phosphate

    • C. 

      Isocitrate

    • D. 

      Pyruvate

    • E. 

      Succinate

  • 129. 
    Which of the following is a coenzyme involved in the conversion of succinate to fumarate in the tricarboxylic acid cycle.
    • A. 

      Acetyle-CoA

    • B. 

      FAD

    • C. 

      NAD

    • D. 

      Lipoic acid

    • E. 

      Biotin

  • 130. 
    The function of the enzyme dihydrolipoyl dehydrogenase (E3) in the pyruvate dehydrogenase complex is to:
    • A. 

      Form a hydroxyethyl derivative of the thiazole ring of enzyme-bound thiamine pyrophosphate

    • B. 

      Transfer an acetyl group from a bound lipoyl group on the enzymes to the thiol of CoA

    • C. 

      Transfer of a hydroxyethyl group of the E-TPP-CHOH-CH3 complex to one of the sulfur atoms of the cyclic disulfide

    • D. 

      Decarboxylate the hydroxyethyl group bound to the thiamine pyrophosphate coenzyme

    • E. 

      Regenerate the oxidized lipoic acid cofactor bound to one of the other enzymes in the complex

  • 131. 
    Coenzymes involved in the reactions of the pyruvate dehydrogenase complex include all of the following except:
    • A. 

      Coenzyme A

    • B. 

      Thiamin pyrophosphate

    • C. 

      NAD

    • D. 

      FAD

    • E. 

      Biotin

  • 132. 
    The essential acidic hydrogen in thiamine is the one which resides
    • A. 

      On the carbon between the nitrogen and sulfur in the thiazolium group in TPP

    • B. 

      On the amino nitrogen in the pyrimidine ring

    • C. 

      On the bridging methylene linkage between the thiazole and the..

    • D. 

      Pyrimidine rings

    • E. 

      On the quaternary nitrogen in the thiazolium group

  • 133. 
    What is a characteristic difference between FAD and NAD+?
    • A. 

      NAD+ is a stronger oxidizing agent than FAD.

    • B. 

      Only FAD participates in oxidation-reduction reactions.

    • C. 

      NAD+ binds tightly to its enzyme while FAD only binds loosely.

    • D. 

      NAD+ transfers two electrons while FAD can transfer one or two

    • E. 

      NAD+ is deoxidising easily be molecular oxygen while FAD is not.

  • 134. 
    During a myocardial infarction, the oxygen supply to an area of the heart is dramaticallyreduced, forcing the cardiac myocytes to switch to anaerobic metabolism. Under theseconditions, which of the following enzymes would be activated by increasing intracellularAMP?
    • A. 

      Succinate dehydrogenase

    • B. 

      Phosphofructokinase-l

    • C. 

      Glucokinase

    • D. 

      Pyruvate dehydrogenase

    • E. 

      Lactate dehydrogenase

  • 135. 
    A 40-year-old black man is seen in the emergency room for a severe headache. His blood pressureis 180/110 mm Hg, and he has evidence of retinal hemorrhage. An infusion of nitroprussideis given. Which of the following enzymes is affected most directly by the active metabolite of thisdrug?
    • A. 

      Phospholipase A2

    • B. 

      Cyclic AMP phosphodiesterase

    • C. 

      Guanylate cyclase

    • D. 

      Cyclic GMP phosphodiesterase

    • E. 

      Phospholipase C

  • 136. 
    When nitroprusside is given in higher than usual doses, it may be accompanied by theadministration of thiosulfate to reduce potential toxic side effects. Which complex associatedwith electron transport or oxidative phosphorylation is most sensitive to the toxicbyproduct that may accumulate with high doses of nitroprusside?
    • A. 

      NADH dehydrogenase

    • B. 

      Succinate dehydrogenase

    • C. 

      Cytochrome b/c1

    • D. 

      Cytochrome a/a3

    • E. 

      F0F1 ATP synthase

  • 137. 
    A patient has been exposed to a toxic compound that increases the permeability of mitochondrialmembranes for protons. Which of the following events in liver cells would youexpect to occur?
    • A. 

      Increased ATP levels

    • B. 

      Increased F1F0ATP synthase activity

    • C. 

      Increased oxygen utilization

    • D. 

      Decreased malate-aspartate shuttle activity

    • E. 

      Decreased pyruvate dehydrogenase activity

  • 138. 
    Which one do you like?
    • A. 

      Option 1

    • B. 

      Option 2

    • C. 

      Option 3

    • D. 

      Option 4

  • 139. 
    The first reaction of the tricarboxylic acid cycle, the citrate synthesis reaction, involves acetyl-CoA reacting with?
    • A. 

      Citrate

    • B. 

      Oxaloacetate

    • C. 

      Isocitrate

    • D. 

      Malate

  • 140. 
    Citrate synthase is a highly regulated enzyme. What is one of the ways this citrate synthesis reaction is driven forward?
    • A. 

      High concentration of NADH

    • B. 

      Low concentration of citrate

    • C. 

      High concentration of succinyl-CoA

    • D. 

      None of the above

  • 141. 
    The succinyl-CoA synthase reaction used succinyl-CoA, a high-energy intermediate, to produce succinate. This reaction also directly produces _______________ in mammals.
    • A. 

      GTP

    • B. 

      ATP

    • C. 

      NADH

    • D. 

      FADH2

  • 142. 
    How many carbon atoms of an acetyl-CoA molecule are lost as CO2 during the first turn of the TCA cycle?
    • A. 

      3

    • B. 

      2

    • C. 

      1

    • D. 

      None

  • 143. 
    Pyruvate carboxylase produces oxaloacetate in response to high levels of acetyl-CoA. Reactions that replenish citric acid cycle intermediates are called _________________ reactions.
    • A. 

      Analplerotic

    • B. 

      Condensation

    • C. 

      Catabolic

    • D. 

      Transketolase

  • 144. 
    The sites of regulation in the citric acid cycle involve reactions with large negative delta G values. These sites of regulation include:
    • A. 

      Citrate synthase and aconitase

    • B. 

      Isocitrate dehydrogenase and citrate synthase

    • C. 

      Fumarase and isocitrate dehydrogenase

    • D. 

      A-ketoglutarate dehydrogenase and aconitase

  • 145. 
    Pyruvate dehydrogenase, which converts pyruvate to acetyl-CoA, is a tightly regulated enzyme in consequence animals can not:
    • A. 

      Synthesize glucose from acetyl-CoA

    • B. 

      Synthesize glucose from pyruvate

    • C. 

      Convert acetyl-CoA to fatty acids

    • D. 

      None of the above

  • 146. 
    Pyruvate dehydrogenase is allosterically inhibited by high levels of:
    • A. 

      Acetyl-CoA

    • B. 

      NADH

    • C. 

      ADP

    • D. 

      A and B

    • E. 

      A and C

  • 147. 
    All are correct statements about the reaction catalysed by citrate synthase EXCEPT:
    • A. 

      Citrate synthase is allosterically activated by ATP

    • B. 

      The complete chemical equation is: Oxaloacetate + acetyl-CoA + H2O --> Citrate + CoA

    • C. 

      Citryl-CoA is formed as an intermediate

    • D. 

      The mechanism involves attack of the carbanion of acetyl-CoA on the carbonyl carbon of oxaloacetate

    • E. 

      The enzyme uses general base catalysis to generate the active species.

  • 148. 
    The following statements are correct about the reaction catalysed by the pyruvate dehydrogenase complex EXCEPT:
    • A. 

      The complex is located in the matrix of the mitochondria.

    • B. 

      The activity of the complex is regulated by the phosphorylation of EI

    • C. 

      NAD+ is the direct oxidant of reduced lipoamide

    • D. 

      An FAD is covalently linked to the E3, the lipoamide dehydrogenase component

    • E. 

      Although EI is called "pyruvate dehydrogenase" it is not a dehydrogenase

  • 149. 
    Order the coenzymes according to their involvement in the pyruvate dehydrogenase complex.1. NAD+2. CoA-SH3. TPP4. Lipoate (lipoamide)5. [FAD]
    • A. 

      1,2,3,4,5

    • B. 

      3,2,1,5,4

    • C. 

      3,4,2,5,1

    • D. 

      2,4,5,1,3

    • E. 

      3,5,4,2,1

  • 150. 
    Citrate must be isomerized to isocitrate because the __________ group of citrate is not oxidizable, but the _________ group of isocitrate can be oxidized.
    • A. 

      Ketone, primary alcohol

    • B. 

      Tertiary alcohol, secondary alcohol

    • C. 

      Ketone, Secondary alchol

    • D. 

      Aldehyde, primary alcohol

    • E. 

      Secondary alcohol, ketone

  • 151. 
    The reaction of malate oxidation to oxaloacetate is not thermodynamically favoured 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 delta G

    • E. 

      The previous reaction has a large negative delta G

  • 152. 
    The cleavage of citrate to acetyl-CoA and oxaloacetate:
    • A. 

      Is a mitochondrial matrix enzyme.

    • B. 

      Requires GTP-> GDP + Pi

    • C. 

      Is catalyzed by citrate synthase

    • D. 

      Is linked with succinyl-CoA as a source of CoA

    • E. 

      Involves an ATP-driven addition of CoA

  • 153. 
    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, acetyle-CoA

  • 154. 
    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

  • 155. 
    Inhibition of the citric acid cycle at isocitrate dehydrogenase increases the levels of citrate and isocitrate that many 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

  • 156. 
    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

  • 157. 
    From the choices listed, indicate the cellular location of the following molecules, enzymes, or processes pyruvate dehydrogenase complex
    • A. 

      Cytoplasm

    • B. 

      The mitochondrial inner membrane space

    • C. 

      The mitochondrial inner membrane

    • D. 

      Matrix of the mitochondria

  • 158. 
    From the choices listed, indicate the cellular location of the following molecules, enzymes, or processes ATP pyruvate 
    • A. 

      Cytoplasm

    • B. 

      The mitochondrial inner membrane space

    • C. 

      The mitochondrial inner membrane

    • D. 

      Matrix of the mitochondria

  • 159. 
    From the choices listed, indicate the cellular location of the following molecules, enzymes, or processes complex IV of the electron transport chain
    • A. 

      Cytoplasm

    • B. 

      The mitochondrial inner membrane space

    • C. 

      The mitochondrial inner membrane

    • D. 

      Matrix of the mitochondria

  • 160. 
    From the choices listed, indicate the cellular location of the following molecules, enzymes, or processes succinate dehydrogenase
    • A. 

      Cytoplasm

    • B. 

      The mitochondrial inner membrane space

    • C. 

      The mitochondrial inne membrane

    • D. 

      Matrix of the mitochondria

  • 161. 
    From the choices listed, indicate the cellular location of the following molecules, enzymes, or processes lactate dehydrogenase
    • A. 

      Cytoplasm

    • B. 

      The mitochondrial inner membrane space

    • C. 

      The mitochondrial inner membrane

    • D. 

      Matrix of the mitochondria

  • 162. 
    • A. 

      A-ketoglutarate

    • B. 

      Succinate

    • C. 

      Fumarate

    • D. 

      Oxaloacetate

  • 163. 
    • A. 

      A-ketoglutarate

    • B. 

      Succinate

    • C. 

      Fumarate

    • D. 

      Malate

  • 164. 
    • A. 

      A-ketoglutarate

    • B. 

      Succinate

    • C. 

      Fumarate

    • D. 

      Both a and b

  • 165. 
    The final electron acceptor in the electron transport chain is
    • A. 

      Molecular O2

    • B. 

      H20

    • C. 

      Cytochrome c

    • D. 

      Ubiquinone

  • 166. 
    In comparing the outer and the inner membranes in the mitochondrion, which statement is incorrect about the inner membrane?
    • A. 

      It is enriched in acidic phospholipids such as diphosphatidyl-glycerol (cardiolipin)

    • B. 

      Its phospholipids are enriched in unsaturated fatty acids

    • C. 

      It has a higher lipid to protein ratio

    • D. 

      It is more highly folded

  • 167. 
    A species in the electron transport chain which can participate in a two-electron transfer is
    • A. 

      Cytochrome

    • B. 

      Protein-bound copper

    • C. 

      Ubiquinone

    • D. 

      Iron-sulfur proteins

  • 168. 
    A species in the electron transport chain which does not have a direct link to ubiquinone in some form is
    • A. 

      Complex IV (oxidase)

    • B. 

      Complex II (reductase)

    • C. 

      Complex I (reductase)

    • D. 

      Complex III (reductase)

  • 169. 
    The species below which is a mobile electron carrier in the electron transport chain is
    • A. 

      FMN

    • B. 

      Fe-S protein

    • C. 

      Cytochrome c

    • D. 

      Cytochrome bc1 complex

  • 170. 
    The complex reduction of one molecule of oxygen (gas) requires how many electrons
    • A. 

      1

    • B. 

      2

    • C. 

      4

    • D. 

      8

  • 171. 
    Another name for complex II in the electron transport chain is 
    • A. 

      Cytochrome c oxidase

    • B. 

      Succinate CoQ reductase

    • C. 

      NADH-CoQ reductase

    • D. 

      Cytochrome bc1complex

  • 172. 
    What molecule is the electron donor to complex III?
    • A. 

      Cytochrome c (Fe2+)

    • B. 

      NADH

    • C. 

      Coenzyme QH2

    • D. 

      H20

  • 173. 
    Intact mitochondria were isolated and used to calculate the P/O ratio of the metabolite a-ketoglutarate. Included in the assay were ADP, inorganic phosphate, NAD+, and malonate in an appropriate buffer. Which statement is correct about this assay system?
    • A. 

      Malonate is included to inhibit the TCA cycle at succinate dehydrogenase

    • B. 

      Only two electrons are removed from a-ketoglutarate under these assay condition

    • C. 

      NADH is the direct donor of the electrons to the electron transport chain in this assay

    • D. 

      All of the above are correct

  • 174. 
    An important difference between CO and CN- in their poisoning effect on an organism that
    • A. 

      CO binds through its carbon atom whereas CN- binds thorugh its nitrogen.

    • B. 

      CN- binds more strongly to the hemoglobin than CO.

    • C. 

      CO binds more strongly to the ATP synthase than CN-

    • D. 

      CN- binds more tightly to the (Fe3+) form of cytochrome oxidase complex than CO.

  • 175. 
    Which of the following is an inhibitor of ATP synthase?
    • A. 

      Rotenone

    • B. 

      Oligomycin

    • C. 

      Antimycin

    • D. 

      Azide

  • 176. 
    A characteristic of the glycerolphosphate shuttle is
    • A. 

      It shuttles NADH across the mitochondrial membrane to yield 2.5 ATP/NADH

    • 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

  • 177. 
    A type of adipose tissue in many organisms is called brown fat. Which of the following statements about brown fat is correct?
    • A. 

      Its color is derived from a high blood supply.

    • B. 

      It produces a great deal of heat as a result of the presence of thermogenin

    • C. 

      Hibernating bears have very little of this type of adipose tissue

    • D. 

      This effciency of oxidative phosphorylation is high in this tissue.

  • 178. 
    Which of the following molecules is least likely to be transported across the inner mitochondrial membrane?
    • A. 

      Citrate

    • B. 

      NADH

    • C. 

      Pyruvate

    • D. 

      Phosphate

  • 179. 
    Complex III (cytochrome reductase) of the mitochondrial electron transport chain has all these properties EXCEPT
    • A. 

      It contains cytochrome b and c1 (as well as other components)

    • B. 

      It accepts electrons but not protons from reduced CoQ

    • C. 

      It donates electrons but not protons to cytochrome c (Fe3+)

    • D. 

      It contains a tightly bound CoQ molecule as part of the complex

  • 180. 
    What statement is incorrect about the addition of an uncoupler such as dinitrophenol to mitochondria which are actively oxidizing pyruvate?
    • A. 

      The uncoupler is usually a weak acid

    • B. 

      It has no effect on the rate of oxygen consumption

    • C. 

      It causes the rate of ADP phosphorylation to decrease

    • D. 

      Upon being protonated, it is soluble in the membrane

  • 181. 
    What statement is incorrect about the mitochondrial ATP-synthesizing complex?
    • A. 

      It contains a transmembrane proton channel

    • B. 

      It contains a spherical headpiece called F1 located on the cytoplasmic side of the inner mitochondrial membrane

    • C. 

      It requires intact inner mitochondrial membranes to synthesize ATP

    • D. 

      The complex hydrolyzes ATP when the inner mitochondrial membranes are disrupted or leaky

  • 182. 
    Consider the standard reduction potentials for the two half reactions below. NAD+ + 2e- + 2H+ -> NADH + H+          E0´ = -320 mV Pyruvate + 2e- + 2H+ -> Lactate             Eo´ = -190 mV which of the following statements is correct about the following reaction? Lactate + NAD+ -> pyruvate + NADH + H+
    • A. 

      NAD+ is a better oxidant than pyruvate

    • B. 

      The reaction has a negative free energy change

    • C. 

      After equal amounts of NAD+, NADH, pyruvate and lactate are mixed and allowed to react, the equilibrium concentration of pyruvate is less that of lactate

    • D. 

      The Eo´ for the reaction is +130 mV

  • 183. 
    Which carrier of the electron transport chain accepts electrons from complex I and donates them to complex III?
    • A. 

      Cyt c

    • B. 

      Cyt b

    • C. 

      Coenzymes Q

    • D. 

      FMN

  • 184. 
    Which statement is incorrect about the glycerolphosphate shuttle?
    • A. 

      There are two distinct forms of glycerol-3-P dehydrogenase in cells

    • B. 

      It results in the net transfer of electrons to the electron transport chain from NADH in the cytoplasm

    • C. 

      Glycerol-3-P is transported across the inner mitochonrial membrane into the matrix

    • D. 

      Electrons derived from this shuttle enter the electron transport chain at a protein complex containing an FAD linked enzyme

  • 185. 
    Which statement of the following is incorrect about the carriers of the electron transport chain in mitochondria?
    • A. 

      Cyt c is a peripheral membrane protein located on the matrix face of the inner mitochondria membrane

    • B. 

      The iron atom of cyt c is reduced when it accepts electrons

    • C. 

      Coenzymes Q is a lipid soluble quinone which accepts electrons and protons from either complex I or II

    • D. 

      Complex I contains a FMN as a component which accepts both electrons and protons

  • 186. 
    The standard reduction potential (Eo´) for the reduction of fumarate to succinate is +0.03 V. The Eo´ for the reduction of FAD is -0.28 V. Which of the following statement is correct about the reaction below? Succinate + FAD -> Fumarate + FADH2
    • A. 

      When equal amounts of succinate, fumarate, FAD and FADH2 are mixed at pH 7.0 in vitro, some FAD becomes reduced.

    • B. 

      The Eo´ for the reaction written above is +0.31 V

    • C. 

      FAD is a better oxidant than fumarate

    • D. 

      The reaction as written is spontaneous (goes to the right) under aerobic condiotions as found in the cell.

  • 187. 
    Which statement is incorrect about the release or consumption of water when pyruvate is oxidized to CO2 in muscle cells?
    • A. 

      A molecule of water is consumed by the reaction catalyzed by citrate synthase

    • B. 

      For each two electrons donated to the electron transport chain, one molecule of water is produced by the reduction of oxygen

    • C. 

      For each ADP phosphorylated, a molecule of water is released from ATP synthase

    • D. 

      Upon complete oxidation to CO2, no net water is made in the cell.