Chapter 14 Bioenergetics and Oxidative Metabolism

Multiple Choice

1. Which of the following enzymes in the tricarboxylic acid cycle requires the same set ofcofactors or coenzymes as the pyruvate dehydrogenase complex?A. alpha-ketoglutarate dehydrogenaseB. isocitrate dehydrogenaseC. succinate dehydrogenaseD. malate dehydrogenaseE. citrate synthaseAns: A2. Which enzyme catalyzes substrate level phosphorylation?A. succinyl-CoA synthaseB. citrate synthaseC. alpha-ketoglutarate dehydrogenaseD. aconitaseE. succinate dehydrogenaseAns: A3. The tricarboxylic acid cycle does not occur in which cells in your body?A. skeletal muscle cellsB. liver parenchymal cellsC. adipose cellsD. renal tubular epitheliumE. erythrocytesAns: E4. All of the following are intermediates of the Krebs cycle EXCEPTA. cis-aconitate.B. pyruvate.C. fumarate.D. succinyl-CoA.E. malate.Ans: B5. Which of the following contains high energy bonds?

A. glucose 6-phosphate.B. creatine phosphate.C. acetoacetate.D. citric acid.E. glutamineAns: B6. The iron in the cytochromes function in biological systems byA. undergoing oxygenation and deoxygenation.B. undergoing oxidation and reduction.C. combining with phosphate.D. undergoing dehydration and hydration.E. interchanging with the iron of adrenodoxin.Ans: B7. The structure of oxidized flavin differs from that of fully reduced flavin byA. one proton.B. one electron and one proton.C. two electrons.D. two protons.E. two electrons and two protons.Ans: E8. M1755lAll of the following concerning the human mitochondrial genetic apparatus aretrue EXCEPTA. the mitochondrial genome is a circular DNA.B. the mitochondrial genome codes for several essential proteins for oxidativephosphorylation.C. the mitochondrial genome exhibits maternal inheritance.D. the mitochondrial genome uses the same genetic code as the nuclear genome.E. a mitochondrial DNA mutation results in Leber's Hereditary Optic Neuropathy.Ans: D9. In order to be considered a high energy compound, a metabolic intermediate must havea free energy of hydrolysis, (delta G0 hydrolysis), equal to, or greater than ______kilocalories / mole.A. + 5.3B. - 5.3C. + 7.3D. - 7.3E. + 9.3

Ans: D10. All of the following reactions are observed in the tricarboxylic acid cycle EXCEPTA. hydration of cis-aconitate to isocitrateB. dehydration of citric acid to form cis-aconitic acidC. oxidative decarboxylation of alpha-ketoglutaric acid to form succinyl-CoAD. hydration of fumaric acid to form malic acidE. decarboxylation of citric acid to form oxalosuccinic acidAns: E11. The mammalian pyruvate dehydrogenase complexA. catalyzes the conversion of pyruvate to acetyl-CoA and carbon dioxide.B. catalyzes the conversion of pyruvate to oxaloacetate.C. functions as a tetramer made up of two types of subunits which are identical to thoseof either muscle (M) or heart (H) origin.D. utilizes NAD as the only required coenzyme.E. catalyzes the oxidation of lactate to pyruvate.Ans: A12. The effect of malonate on succinate dehydrogenase isA. noncompetitive inhibition.B. competitive inhibition.C. irreversible inhibition.D. uncompetitive inhibition.E. no inhibition; it is the product of the reaction.Ans: B13. The prosthetic group in mitochondrial cytochromes isA. FeSB. NADC. hemeD. flavinE. ADPAns: C14. The free energy change for a reaction at equilibrium isA. less than 1.B. zero.C. greater than 1.D. equal to -RT 1n Keq.E. can be utilized to do work in the cell.

Ans: B15. The enzymes of the respiratory chain areA. in the cytosol.B. on the outer membrane of the mitochondria.C. on the inner membrane of the mitochondria.D. in the mitochondrial matrix.E. in the lysosomes.Ans: C16. How is uncoupling produced in brown adipose tissue?A. Action of thyroid hormone on a mitochondrial thyroid receptorB. Activation of UCP-1 by fatty acidsC. Induction of ATPaseD. Synthesis of a small non-protein uncoupling moleculeE. Transfer of protons out of the mitochondrial matrixAns: B17. Oligomycin inhibits oxidative phosphorylation by:A. Binding to cytochromesB. Channeling protonsC. Binding to coenzyme QD. Oxidizing FADE. Inhibiting phosphorylationAns: E18. Which coenzyme is NOT required for the activity of the pyruvate dehydrogenasecomplex?A. biotinB. lipoic acidC. thiamine pyrophosphateD. coenzyme AE. flavin adenine dinucleotideAns: A19. Anaplerotic reactionsA. are generally endergonic.B. are typified by that catalyzed by pyruvate kinase.C. are defined as reactions which produce pyruvate.D. increase the concentrations of intermediates of the Krebs cycle.E. are typified by those catalyzed by pyruvate dehydrogenase and alpha-ketoglutaratedehydrogenase.

Ans: D20. An allosteric activator of mitochondrial NAD-linked isocitrate dehydrogenase isA. alpha-ketoglutarate.B. ADP.C. NADH.D. acetyl-CoA.E. glucose 6-phosphate.Ans: B21. The chemiosmotic hypothesis suggests that the potential energy of the electronsmoving down the mitochondrial electron transport chain from a negative to a positiveoxidation potential is initially conserved in the form of aA. proton gradient across the membrane.B. a high energy phosphate bond.C. a different conformational form of the electron carriers.D. a protonated form of coenzyme Q.E. a reduced non-heme iron protein.Ans: A22. All of the following statements about oxidative phosphorylation are correct EXCEPTA. ATP synthesis is driven by a pH gradient and a membrane potential.B. ATP synthase translocates ATP through mitochondrial membrane.C. the respiratory chain consists of three enzyme complexes linked by two mobileelectron carriers.D. the process can be uncoupled by 2,4-dinitrophenol.Ans: B23. The definition of a high energy bond is a bondA. with a high chemical bond energy.B. which is highly unstable.C. which is highly exergonic.D. with a high phosphate group transfer potential.E. with a large negative free energy change on hydrolysis.Ans: E24. In the Q cycle for electron transfer and protein pumping in Complex III of themitochondrial electron transport chain, how many proteins are taken up from the matrixside of the inner membrane and how many are released into the inner membrane spacerespectively?A. 1 and 2

B. 2 and 2C. 2 and 4D. 4 and 2E. 4 and 4Ans: C25. Respiratory control refers to the striking dependence of respiration on the availabilityofA. O2B. GlucoseC. ADPD. ATPE. electronsAns: C26. All of the following molecules, without further metabolism, can cross the innermembrane of functioning mitochondria EXCEPTA. ATP.B. oxygen.C. inorganic phosphate.D. pyruvate.E. acetyl CoA.Ans: E27. The enzyme which catalyzes the entrance of acetyl CoA into the Krebs cycle isA. aconitase.B. citrate synthase.C. succinate thiokinase.D. pyruvate dehydrogenase.E. isocitric dehydrogenase.Ans: B28. A simple explanation of the action of an uncoupler of mitochondrial oxidativephosphorylation is that it is any agent thatA. blocks the oxidation of reduced cytochrome c by cytochrome oxidase.B. prevents formation of ATP by interacting with and blocking proton transport throughthe proton translocating ATPase.C. acts to conduct protons back into the mitochondrial matrix without accompanyingformation of ATP.D. blocks proton conductance and slows oxygen uptake rates.Ans: C

29. A simple explanation of the action of an uncoupler of mitochondrial oxidativephosphorylation is that it is any agent thatA. blocks the oxidation of reduced cytochrome c by cytochrome oxidase.B. prevents formation of ATP by interacting with and blocking proton transport throughthe proton translocating ATPase.C. acts to conduct protons back into the mitochondrial matrix without accompanyingformation of ATP.D. blocks proton conductance and slows oxygen uptake rates.Ans: C30. What effect does the chemical uncoupler 2,4-dinitrophenol have on mitochondria?A. inhibits electron transport and oxidative phosphorylationB. allows electron transport to proceed without ATP synthesisC. blocks the transfer of electrons from NADH to O2D. stimulates ATP synthesisE. blocks the transfer of electrons from complex I to complex II.Ans: B31. What thermodynamic parameters are compatible with the spontaneity of a chemicalreaction?A. positive standard free energy change only.B. positive standard free energy change and high activation energy.C. negative standard free energy change and high activation energy.D. positive standard free energy change and low activation energy.E. negative standard free energy change.32. How does the binding-change model for synthesis and hydrolysis of ATP in theinner mitochondrial membrane work??A. Flipping of orientation of F1Fo-ATP synthase in the membraneB. A one-step rotation of 180oC. Change in the binding constant for ATP on the T subunitD. Conformation change of the b subunit resulting in release of protonsE. Rotation of the g subunit in 120o stepsAns: E33. Employs a flavoprotein:A. Glucose production from glycogenB. Lactate production from glucoseC. Malate production from succinyl CoAD. pyruvate production from fructoseE. Succinate production from succinyl CoA

Ans: C34. Which of the following enzyme systems is most analogous to the pyruvatedehydrogenase complex?A. oxaloacetate dehydrogenaseB. succinate dehydrogenaseC. fumaraseD. isocitrate dehydrogenaseE. alpha-ketoglutarate dehydrogenaseAns: E35. Oxaloacetate moves through the mitochondrial membraneA. after conversion to glycerol phosphate.B. by passive diffusion.C. after reaction with carnitine.D. after oxidation to pyruvate.E. after reduction to malate.Ans: E36. Certain bacterial mutant lacks the kinase catalyzing the reaction ATP + GDP ADP + GTP but otherwise possesses enzymes similar to those in mammals. This mutantcould still produce GTP from GDP by utilizing the enzymeA. phosphoglycerate kinase.B. pyruvate kinase.C. pyruvate carboxylase.D. creatine kinase.E. succinate thiokinase.Ans: E37. The electron transport chain of mitochondria is specifically located in theA. outer membrane.B. intermembrane space.C. inner membrane.D. matrix.E. tonoplast.Ans: C38. Which of the following is the only mobile electron carrier in the electron transportsystem that is neither permanently associated nor covalently attached to a protein?A. FMNB. coenzyme QC. heme a3

D. FeS clusterE. FADAns: B39. Which of the following is a potential oxidant?A. FADB. NADPHC. NADHD. ATPE. Fe2+Ans: A40. What is the most visible sign of reactive oxygen species damage?A. Age spotsB. CataractsC. Dental cariesD. Hair lossE. OsteoporosisAns: A41. Substrate level phosphorylation in mitochondriaA. Consumes ATPB. Consumes NADHC. Is catalyzed by a flavoproteinD. Produces coenzyme AE. Produces fumarateAns: D42. A number of intermediates in lipid metabolism are esters of coenzyme A. The vitaminprecursor of coenzyme A isA. beta-carotene.B. biotin.C. nicotinic acid.D. pantothenic acid.E. riboflavin.Ans: D43. The activity of pyruvate dehydrogenase (PDH) decreasesA. as the concentration of acetyl CoA decreases.B. as the concentration of NAD increases.C. when the dephospho-enzyme is converted to its phospho form.

D. as the concentration of pyruvate increases.E. as the concentration of AMP increases.Ans: C44. Which is a flavoprotein?A. isocitrate dehydrogenaseB. succinate dehydrogenaseC. carbonic anhydraseD. citrate synthaseE. aconitaseAns: B45. A major control point of the Krebs cycle is exerted at the level ofA. succinate dehydrogenase.B. citrate synthase.C. succinyl CoA synthase.D. malate dehydrogenase.E. aconitase.Ans: B46. The uncoupling of oxidative phosphorylation in the human might be of physiologicalimportance because itA. allows storage of nutrients.B. produces water.C. increases carbon dioxide level in the blood.D. produces heat.E. raises the oxygen level in the blood.Ans: D47. Which of the statements below is correct for the reaction NADH + FMN + H+ --->NAD+ + FMNH2A. the reaction involves only the transfer of a hydrogen atom.B. NAD+ is the oxidant.C. FMNH2 is the electron acceptor.D. FMN is the reducing agent.E. NADH is the electron donor.Ans: E48. Which molecule is involved in the major step for the production of superoxide in themitochondrial electron transport chain?A. cytochrome c

B. cytochrome oxidaseC. NADH dehydrogenaseD. Succinate dehydrogenaseE. UbiquinoneAns: E49. A substrate with a P:O ratio of 1.5 is:A. Alpha-ketoglutarateB. IsocitrateC. MalateD. pyruvateE. SuccinateAns: E50. Each of the following statements concerning mitochondrial protein synthesis are trueEXCEPT which one?A. Mitochondrial protein synthesis is inhibited by chloramphenicol.B. The enzymes of the respiratory chain are all coded by mitochondrial genes.C. Mitochondrial protein synthesis is initiated by N-formylmet-tRNA fmet.D. The mitochondrial genome codes for only certain proteins of the inner mitochondrialmembrane.E. Protein synthesis in mitochondria is closely integrated with cytoplasmic proteinsynthesis.Ans: B51. Which statement about the pyruvate dehydrogenase complex is true?A. Lipoamide functions in the decarboxylation of pyruvate.B. Coenzyme A is covalently bound to a lysine residue in one of the proteins of thecomplex.C. phosphorylation catalyzed by a kinase results in decreased activity.D. NADH is an allosteric activator of pyruvate oxidation.E. The function of FAD is to oxidize NADH.Ans: C52. Which enzyme occurs in mammals in both NAD- and NADP-linked forms?A. isocitrate dehydrogenaseB. succinate dehydrogenaseC. alpha-ketoglutarate dehydrogenaseD. citrate synthaseE. aconitaseAns: A

53. How many molecules of NAD are reduced as one molecule of pyruvate ismetabolized through one turn of the Krebs cycle?A. 1B. 2C. 3D. 4E. 5Ans: D54. Cyanide is toxic because it inhibitsA. succinate dehydrogenase.B. NADH-dehydrogenase.C. phosphorylase.D. pyruvate dehydrogenase.E. cytochrome oxidase.Ans: E55. In liver cells, substrate-level phosphorylation may be differentiated frommitochondrial oxidative phosphorylation in that all substrate-level phosphorylationA. can continue in the presence of dinitrophenol.B. requires inorganic phosphate.C. forms GTP as the immediate product.D. requires a proton gradient.E. is characterized by all of the above.Ans: A56. A reaction between hydrogen peroxide and superoxide can produce hydroxyl radicals.What else can cause hydrogen peroxide to form this toxic species?A. Fe2+B. K+C. Mg2+D. Mn2+E. Na+Ans: A57. How does lack of oxygen in the cell decrease TCA cycle activity?A. synthesis of lactic acid from pyruvate is inhibitedB. increased malonyl CoA inhibits carnitine acyl transferase I.C. electron transport cannot be used to regenerate NAD+D. epinephrine levels are increasedE. glycogenolysis is decreased, causing less requirement for the TCA cycle.

Ans: C58. The formation of GTP in the citric acid cycle is an example ofA. phosphorolysis.B. oxidation.C. oxidative phosphorylation.D. reduction.E. substrate level phosphorylation.Ans: E59. Which reaction in the citric acid cycle requires the participation of lipoic acid andthiamine pyrophosphate?A. acetyl CoA + oxaloacetate ----> citrateB. citrate ----> isocitrateC. isocitrate ----> alpha-ketoglutarateD. alpha-ketoglutarate ----> succinyl CoAE. succinyl CoA ----> succinateAns: D60. Oxaloacetate is a substrate of which enzyme?A. isocitrate dehydrogenaseB. succinate dehydrogenaseC. fumaraseD. citrate synthaseE. aconitaseAns: D61. The ratio of NADH/NAD is greatest inA. microsomes.B. mitochondria.C. nucleus.D. cytosol.Ans: B62. All of the following items are requirements of the chemiosmotic mechanism ofoxidative phosphorylation EXCEPTA. a topologically closed, proton impermeable membrane.B. an ATPase which can be driven in reverse by a proton gradient across the membrane.C. a proton translocating system oriented asymmetrically across the membrane.D. a direct coupling of electron transport to phosphorylation.

Ans: D63. An enzyme which catalyzes the conversion of hydrogen peroxide to water andoxygen isA. catalase.B. invertase.C. peroxide mutase.D. a cytochrome.E. glutathione peroxidase.Ans: A64. What is the most reactive form of oxygen?A. H2OB. H2O2C. O2D. O2.-E. OH.Ans: E65. In tightly coupled mitochondria, the rate of oxidative phosphorylation is governed bythe concentration ofA. Acetyl-CoAB. PiC. ADPD. ATPE. NADPHAns: C66. Which of the following would NOT be considered a high energy compound?A. ATPB. phosphoenolpyruvateC. ADPD. 1,3-bisphosphoglycerateE. glyceraldehyde 3-phosphateAns: E67. Which is the immediate product of an anaplerotic reaction related to the Krebs cycle?A. citrateB. malateC. oxaloacetateD. acetyl CoAE. pyruvate

Ans: C68. All enzymes of the Krebs cycle, except for succinate dehydrogenase, are found in theA. mitochondrial matrix.B. inner mitochondrial membrane.C. intermembrane space.D. outer mitochondrial membrane.E. cytosol.Ans: A69. Which is a tricarboxylic acid?A. oxaloacetateB. succinateC. alpha-ketoglutarateD. citrateE. acetateAns: D70. Oligomycin has a direct inhibitory effect onA. the adenine nucleotide exchange protein.B. ATP synthase.C. site I of the respiratory chain.D. site II of the respiratory chain.E. site III of the respiratory chain.Ans: B71. All of the following statements about cytochrome c are correct EXCEPT which one?A. The reduced form of the protein participates in electron transport by directly donatingelectrons to oxygen.B. Unlike the other mitochondrial cytochromes, it is water soluble.C. It contains iron which undergoes reversible oxidation and reduction during electrontransport.D. It is visibly colored.E. It is reduced by the reduced form of the cytochrome bc1 complex.Ans: A72. A typical enzyme-catalyzed reduction reaction occurring in a biosynthetic pathwaywould require the cofactorA. NAD+B. FADH2C. FAD

D. NADPHE. NADP+Ans: D73. Which of the following would NOT have an inhibitory effect on the flow ofmetabolites through the citric acid cycle?A. High levels of ATP relative to ADPB. Depletion of NADH by its conversion to NAD+C. Limited availability of oxaloacetateD. High levels of citrateE. Depletion of acetyl-CoAAns: B74. Electrons from NADH produced in the cytosol by glycolysis may be transported intothe mitochondrion and to the electron transport chain through which of the followingcompounds?A. glutamateB. lactateC. malateD. oxaloacetateE. pyruvateAns: C75. How many moles of ATP can be formed from ADP during the complete oxidation ofone mole of pyruvate to carbon dioxide and water in normal liver cells?A. 3B. 9C. 12D. 15E. 36Ans: D76. Oxidation of one molecule of pyruvate by the combined action of the pyruvatedehydrogenase complex and the enzymes of the citric acid cycle is thought to result in thegeneration of how many pairs of electrons which can move through the electron transportchain?A. 3B. 4C. 5D. 6E. 7

Ans: C77. Succinate dehydrogenase is found in which subcellular fraction of the liver?A. microsomesB. mitochondrial matrixC. Golgi apparatusD. inner membrane of the mitochondrionE. cytosolAns: D78. Cytochrome a, a3 (cytochrome oxidase)A. contains copper which is required for the reduction of oxygen.B. is a terminal electron acceptor which forms hydrogen peroxide upon reduction ofoxygen.C. can be reduced directly by cytochrome b.D. is not inhibited by carbon monoxide.E. is inhibited directly by rotenone and amytal.Ans: A79. In ATP, the linkage between each of the phosphate groups is aA. phosphomonoester.B. phosphodiester.C. phosphoamide.D. phosphoanhydride.E. phosphoenol.Ans: D80. A radical is a molecule with a highly reactive unpaired electron in the outer shell.What does it need to attain its preferred state?A. A pair of electronsB. A protonC. Another electronD. Loss of a proteinE. Loss of the single electronAns: C81. The steady-state activity of pyruvate dehydrogenase (PDH) is reduced by increases inall of the following EXCEPTA. acetyl CoA.B. NADH.C. cyclic AMP.D. ingestion of ethanol.

E. ATP.Ans: C82. All of the following are found in, or associated with the mitochondrial electrontransport chain EXCEPTA. cytochromes.B. coenzyme Q (ubiquinone).C. proteins containing non_heme iron and sulfur.D. proteins containing FMN.E. substrate level phosphorylation.Ans: E83. The initial step in the reactions catalyzed by the pyruvate dehydrogenase complex isthe formation of carbon dioxide andA. lipoic acid in its reduced form.B. acetyl-CoA.C. the reduction of NAD+.D. a two carbon unit covalently linked to thiamine pyrophosphate.E. citrate.Ans: D84. The glycerol phosphate shuttle results in the transport of which of the following fromthe cytosol into the mitochondrial matrix?A. NAD+B. NADHC. glycerol-3-phosphateD. dihydroxyacetone phosphateE. electronsAns: E85. The enzyme in the citric acid cycle that catalyzes the conversion of GDP + Pi -->GTP isA. fumarase.B. isocitrate dehydrogenase.C. malate dehydrogenase.D. succinate dehydrogenase.E. succinyl-CoA synthetase.Ans: E86. NADH can reduce coenzyme Q through the mediation of an enzyme associated withwhich of the following?

A. cytochrome cB. Lipoic acidC. Iron-PorphyrinD. cytochrome aE. FMNAns: E87. Uncouplers of oxidative phosphorylationA. increase ATP synthesis.B. decrease oxygen consumption.C. decrease substrate oxidation.D. short circuit a proton gradient.E. include substances such as penicillin.Ans: D88. All of the following are components of the mitochondrial electron transport chainEXCEPTA. cytochrome c.B. thiamine pyrophosphate.C. coenzyme Q.D. cytochrome b.E. flavoprotein.Ans: B89. There cannot be significant net formation of glucose from stearic acid in a mammalbecause of the irreversibility of the reaction catalyzed byA. pyruvate kinase.B. pyruvate carboxylaseC. hexokinase.D. pyruvate dehydrogenase.E. glucose 6-phosphate dehydrogenase.Ans: D90. The synthesis of ATP in oxidative phosphorylation occurs at which of the followinglocations in the cell?A. cytosolB. plasma membraneC. outer membrane of the mitochondrionD. inner membrane of the mitochondrionE. nuclear membraneAns: D

91. All of these vitamins are essential for the activity of mammalian pyruvatedehydrogenase EXCEPTA. thiamine.B. pyridoxine.C. niacin.D. pantothenic acid.E. riboflavin.Ans: B92. M17192Lipoamide is a carrier of activatedA. acyl groups.B. aldehydesC. carboxylatesD. methyl groupsE. phosphoryl groupsAns: A93. All of the following metabolites are oxidized by an NAD-linked enzyme in liver cellsEXCEPTA. isocitrate.B. malate.C. lactate.D. succinate.E. glyceraldehyde 3-phosphate.Ans: D94. The locus for rotenone inhibition of mitochondrial metabolism isA. malate dehydrogenase.B. NADH dehydrogenase.C. cytochrome oxidase.D. ATPase.E. succinate dehydrogenase.Ans: B95. All of the following statements are consistent with the chemiosmotic hypothesis ofoxidative phosphorylation EXCEPT which one?A. Agents which uncouple oxidative phosphorylation from electron transport disruptpermeability barriers such that mitochondrial membranes become permeable to protons.B. The term electrochemical gradient or proton gradient operationally describes the freeenergy generated by electron transport which drives phosphorylation of ADP.

C. Protons are transferred into the mitochondria during electron transport establishing apH gradient.D. Intact mitochondrial membranes are necessary for oxidative phosphorylation tooccur.E. electron carriers of the electron transport chain are vectorially oriented.Ans: C96. All of the following enzymes require a niacin-derived coenzyme EXCEPT whichone?A. pyruvate dehydrogenaseB. Glyceraldehyde 3-phosphate dehydrogenaseC. Malate dehydrogenaseD. Glucose 6-phosphate dehydrogenaseE. Mitochondrial glycerol phosphate dehydrogenaseAns: E97. Has the LEAST involvement in the oxidative burst:A. Glucose-6-phosphate dehydrogenaseB. Glutathione peroxidaseC. MyeloperoxidaseD. NADPH oxidaseE. Superoxide dismutaseAns: B98. Thermogenesis in brown adipose tissue could not occur without increasedA. calcium levels in the cytoplasm.B. secretion of ketone bodies into blood.C. uncoupling protein in the mitochondria.D. oxidation of glucose.E. synthesis of triacylglycerols.Ans: C99. Syntheses and release of ATP in the mitochondrion from the F1_ATPase is driven byA. the discharge of a proton gradient between the intermembrane space and the matrix ofthe mitochondrion.B. the discharge of a proton gradient between the cytosol and the intermembrane space.C. the direct formation of a high energy compound in electron transport.D. the reduction of oxygen at the end of the electron transport chain.E. the discharge of a sodium gradient between the intermembrane space and themitochondrial matrix.Ans: A

100. Which reaction of the Krebs cycle is not physiologically reversible?A. the formation of citrate from oxaloacetateB. the oxidation of succinateC. the oxidation of malateD. the reduction of fumarateE. the reduction of oxaloacetateAns: A101. A flavoprotein is required for theA. formation of glucose from glycogen.B. production of lactate from glucose.C. production of malate from succinyl CoA.D. production of pyruvate from fructose.E. production of succinate from succinyl CoA.Ans: C102. All of the following must be catabolized to acetyl CoA before entering the Krebscycle EXCEPTA. palmitate.B. glucose.C. lactate.D. alanine.E. glutamate.Ans: E103. All of the following compounds would inhibit the oxidation of pyruvate by intactliver mitochondria EXCEPTA. sodium cyanide.B. rotenone.C. antimycin A.D. 2,4-dinitrophenol.E. oligomycin.Ans: D104. Myokinase catalyzes the reaction: ADP + ADP ATP + AMP. From yourknowledge of high energy bonds, predict the equilibrium constant for this reaction.A. 1.C. approximately 1.D. 0.E. none of the above.

Ans: C105. Which does NOT occur among the reactions catalyzed by the pyruvatedehydrogenase complex of liver mitochondria?A. the transfer of an acetyl group to coenzyme A.B. the reduction of a disulfide.C. formation of an acetyl derivative of lipoic acid.D. a redox reaction involving coenzyme Q.E. formation of a covalent bond between a two-carbon unit and thiamine pyrophosphate.Ans: D106. Which Krebs cycle intermediate helps to regulate the overall rate of glycolysis bydirect influence on the activity of phosphofructokinase?A. citrateB. succinateC. alpha-ketoglutarateD. oxaloacetateE. malateAns: A107. The citric acid cycle is slowed by which of the following?A. ADP and AMPB. oxaloacetate and ADPC. NAD+ and ADPD. NADH and ATPE. NAD+ and oxaloacetateAns: D108. The main function of the glycerol phosphate shuttle is inA. anaerobic glycolysis for regeneration of NAD.B. the beta-oxidation of fatty acids.C. the transport of reducing equivalents into mitochondria from NADH formed duringglycolysis.D. the biosynthesis of triacylglycerols.E. the biosynthesis of serine for use in mitochondrial protein synthesis.Ans: C109. An intermediate in the Krebs cycle which is an immediate precursor of CO2 isA. malate.B. citrate.C. isocitrate.

D. aconitate.E. succinate.Ans: C110. Which statement about the mammalian pyruvate dehydrogenase complex isFALSE?A. The complex functions in the matrix of mitochondria.B. The complex contains three different enzyme activities.C. The complex contains five different coenzymes.D. The complex is not regulated by phosphorylation- dephosphorylation.E. Lipoic acid is covalently bound to one of the proteins of the complex.Ans: D111. Oxidative phosphorylation in the mitochondrion is carried out by enzymesA. in the outer membrane.B. in the inner membrane.C. in the matrix.D. in the intermembrane space.E. All of the above.Ans: B112. Which has the most POSITIVE reduction potential?A. NADP/NADPHB. cytochrome c/reduced cytochrome cC. FAD/FADH2D. NAD/NADHE. O2/H2OAns: E113. The oxidation of NADH involves the removal ofA. one hydrogen atom.B. one electron.C. two electrons.D. a hydride ion.E. one proton and one electron.Ans: D114. Which of the following enzymes is important in protecting the cell from thepotential toxicity of superoxide anion and its derivatives?A. superoxide dismutaseB. cytochrome oxidase

C. succinate dehydrogenaseD. FoF1-ATPaseAns: A115. The electron transport, which occurs at the inner membrane of the mitochondrionand leads to the synthesis of ATP, results in which of the following processes?A. pumping of protons from the matrix of the mitochondrion to the intermembrane space.B. pumping of protons from the intermembrane space into the matrix of themitochondrion.C. pumping of electrons from the matrix of the mitochondrion to the intermembranespace.D. pumping of electrons from the intermembrane space into the matrix of themitochondrion.Ans: A116. Which enzyme of the Krebs cycle requires free coenzyme A as a substrate?A. citrate synthaseB. succinyl-CoA synthetaseC. succinic dehydrogenaseD. alpha-ketoglutarate dehydrogenaseE. isocitrate dehydrogenaseAns: D117. If acetyl-CoA, uniformly labeled with 14C in the acetyl group, is condensed withunlabeled oxaloacetate and the product is oxidized via the Krebs cycle, how much of theoriginal radioactivity will be found in the oxaloacetate formed after one turn of the cycle?A. 100%B. 75%C. 50%D. 25%E. 0%Ans: A118. All of the following are enzymes of the Krebs cycle EXCEPTA. isocitrate dehydrogenase.B. alpha-ketoglutarate dehydrogenase.C. enolase.D. succinate thiokinase.E. succinate dehydrogenase.Ans: C

119. When a high energy compound undergoes hydrolytic cleavage, there is a(an)A. large increase in internal bond energy.B. decrease in resonance.C. lowering of the redox potential.D. large decrease in free energy content between reactant and products.E. increase in the equilibrium constant.Ans: D120. The main function of the mitochondrial electron transport chain is toA. generate a P/O ratio of 3.B. recycle NAD for glycolysis.C. provide reducing equivalents.D. lower the oxidation state of the cell.E. generate energy for ATP formation.Ans: E121. Which type of enzyme can supply the citric acid cycle with oxaloacetate frompyruvate?A. an isomeraseB. a mutaseC. a ligaseD. a kinaseE. a lyaseAns: C122. Mitochondrial genes code for 13 proteins, 2 rRNAs, and tRNAs. For whichmultisubunit protein do these genes encode the most proteins?A. ATP synthaseB. cytochrome c reductaseC. NADH-ubiquinone oxidoreductaseD. Succinate dehydrogenaseE. Ubiquinol-cytochrome c oxidoreductaseAns: C

Chapter 15 Carbohydrate Metabolism I: Major Metabolic Pathways and Their Control

Multiple Choice

1. The activity of which enzyme would be expected to increase as levels of insulinincrease?A. pyruvate dehydrogenaseB. pyruvate carboxylaseC. glucose 6-phosphataseD. glycogen phosphorylaseE. PEP carboxykinaseAns: A2. Lack of activity of hepatic phosphoglucomutase in a non- fasting subject is most likelyto produce a deficiency ofA. pyruvate.B. ribose 5-phosphate.C. NADP.D. NADH.E. glycogen.Ans: E3. Biotin participates in the reaction catalyzed byA. phosphoenolpyruvate carboxylase kinase.B. pyruvate carboxylase.C. pyruvate dehydrogenase.D. pyruvate kinase.E. lactate dehydrogenase.Ans: B4. Which of the enzymes below acts in the conversion of glucose -6-phosphate to fructose-6-phosphate?A. kinaseB. isomeraseC. phosphataseD. mutaseE. dehydrogenaseAns: B

5. All of the following are involved in some aspect of galactose metabolism EXCEPTA. an epimerase.B. a uridyltransferase.C. glucose 1-phosphate phosphatase.D. UDP-glucose.E. a pyrophosphorylase.Ans: C6. In the glycolytic pathway for conversion of glucose to lactate, an immediate product ofthe reaction catalyzed by aldolase isA. fructose 2,6-bisphosphate.B. fructose 2-phosphate.C. 3-phosphoglycerate.D. dihydroxyacetone phosphate.E. 1,3-diphosphoglycerate.Ans: D7. Glycogen phosphorylase catalyzes the following reaction Inorganic phosphate +glycogen (n) -->glucose -phosphate + glycogen (n-) To which enzyme class does itbelong?A. transferaseB. ligaseC. hydrolaseD. lyaseE. isomeraseAns: A8. Which of the following compounds is a key intermediate in gluconeogenesis fromlactate, pyruvate, alanine, and glutamic acid?A. ornithineB. citrateC. acetyl-CoAD. oxaloacetateE. malonyl-CoAAns: D9. The net products of anaerobic glycolysis areA. ATP, lactateB. ATP, pyruvateC. NAD, lactateD. ATP, acetyl-CoA

Ans: A10. A deficiency of hepatic phosphoglucomutase would most likely lead to a deficiencyof which one of the following cellular componentsA. pyruvate.B. ribose 5-phosphateC. NADPD. NADHE. glycogenAns: E11. Epinephrine stimulates the formation ofA. AMP.B. the inactive, dephosphorylated form of glycogen synthase.C. the active, phosphorylated form of phosphorylase.D. phosphodiesterase.E. hexokinase.Ans: C12. Which of the following reactions IS NOT INVOLVED in regulation of thephosphorylase kinase cascade?A. formation of cyclic AMP.B. activation of protein kinase.C. phosphorylation of certain amino acids of phosphorylase kinase.D. proteolysis.E. phosphatases.Ans: D13. An enzyme catalyzing an anaplerotic reaction isA. pyruvate dehydrogenase.B. glucose 6-phosphatase.C. thiolase.D. citrate synthase.E. pyruvate carboxylase.Ans: E14. The substrates for the phosphoenolpyruvate carboxykinase reaction areA. alanine and GTP.B. oxaloacetate and GTP.C. oxaloacetate and ATP.D. phosphoenolpyruvate and GTP.

E. pyruvate and GTP.Ans: B15. The substrate for the committed step in glycolysis isA. glucoseB. fructose 6-phosphateC. glucose 6-phosphateD. fructose 1,6-bisphosphateE. fructose 2,6-bisphosphateAns: B16. The glucose-alanine cycle serves toA. transport carbons from skeletal muscle to the liver.B. transport nitrogen from liver to skeletal muscle.C. transport carbons and nitrogen from skeletal muscle to the liver.D. transport carbons and nitrogen from liver to skeletal muscle.E. transport glucose from skeletal muscle to liver.Ans: C17. Which metabolic process is most markedly impaired in the ABSENCE of insulin?A. Degradation of glycogen to glucose.B. Use of acetoacetic acid for energy.C. Transport of glucose through the muscle cell membranes.D. Reabsorption of glucose by the renal tubules.Ans: C18. Skeletal muscle glycogen is not a source of blood glucose because skeletal muscledoes not containA. glucose 6-phosphate dehydrogenase.B. phosphorylase.C. phosphoglucomutase.D. glucokinase.E. glucose 6-phosphatase.Ans: E19. The malate-aspartate shuttle results in the reduction of intramitochondrialA. dihydroxyacetone phosphate.B. pyruvate.C. NAD.D. glycerol-3-phosphateE. all of the above.

Ans: C20. Which enzyme is not subject to allosteric regulation?A. phosphofructokinaseB. hexokinaseC. pyruvate kinaseD. glycogen synthaseE. glucose 6-phosphataseAns: E21. Which statement regarding the control of glycogen metabolism by cyclic AMP isTRUE?A. Cyclic AMP binds allosterically to both glycogen phosphorylase and glycogensynthase, activating the former and inactivating the latter.B. Cyclic AMP stimulates the phosphorylation of glycogen phosphorylase and glycogensynthase, activating both.C. Cyclic AMP stimulates the phosphorylation of glycogen phosphorylase and thedephosphorylation of glycogen synthase, activating the former and deactivating thelatter.D. Cyclic AMP stimulates the phosphorylation of both glycogen phosphorylase andglycogen synthase, activating the former and deactivating the latter.E. Cyclic AMP increases the intracellular concentration of calcium ions whichstimulates the dephosphorylation of both glycogen phosphorylase and glycogensynthase.Ans: D22. Which of the following employs the enzyme phosphoenolpyruvate carboxykinase?A. glycolysisB. Hexose monophosphate shuntC. Krebs cycleD. gluconeogenesisE. glycogenolysisAns: D23. Which process is NOT increased in the presence of insulin?A. gluconeogenesis in liverB. glucose transport into adipose tissueC. protein synthesis in muscleD. lipogenesis in adipose tissueE. glycogen synthesis in muscleAns: A

24. Increased levels of ATP inhibit which pair of enzymes?A. glyceraldehyde 3-phosphate dehydrogenase and enolaseB. lactate dehydrogenase and triose phosphate isomeraseC. phosphofructokinase and pyruvate kinaseD. phosphofructokinase and glucose 6-phosphate isomeraseE. glucokinase and phosphoglucomutaseAns: C25. All of the following enzymes have been shown to be defective in one of the glycogenstorage diseases EXCEPT which one?A. glucose 6-phosphataseB. pyruvate kinaseC. phosphorylaseD. branching enzyme (alpha-1,4 --> alpha-1,6)Ans: B26. A true statement concerning phosphofructokinase- (PFK-) and fructose-,-bisphosphatase is thatA. PFK-1 catalyzes the fastest step in glycolysis.B. PFK-1 catalyzes a reversible step in both glycolysis and gluconeogenesis.C. PFK-1 is not found in red blood cells.D. Fructose-1,6-bisphosphatase requires ATP for energy.E. Fructose-2,6-bisphosphate is a positive allosteric regulator of PFK-1 and is a negativeallosteric regulator of fructose-1,6-bisphosphatase.Ans: E27. All of the following sugars require the action of phosphofructokinase for theirmetabolism to carbon dioxide and water EXCEPTA. glucose.B. galactose.C. mannose.D. maltose.E. fructose.Ans: E28. Two allosterically regulated enzymes on the pathway from lactate to glucose areA. phosphofructokinase and pyruvate kinaseB. pyruvate carboxylase and fructose 1,6-bisphosphataseC. fructose 1,6-bisphosphatase and glyceraldehyde 3-phosphate dehydrogenaseD. pyruvate dehydrogenase and pyruvate carboxylase

Ans: B29. All of the following statements about glycolysis and gluconeogenesis are trueEXCEPT which one?A. High concentrations of acetyl-CoA inhibit acetyl-CoA formation from pyruvate andhigh concentrations of acetyl-CoA stimulate carboxylation of pyruvate.B. When citrate concentrations in the cytosol are high, PFK-1 activity is inhibited andfructose-1,6-bisphosphatase activity is stimulated.C. Oxaloacetate is formed from acetyl CoA.D. Formation of glucose from glycerol does not require the involvement ofmitochondria.E. NADH2 is required for the formation of glucose from pyruvate.Ans: C30. In fructose metabolism in the liver, the action of fructokinase on fructose results inthe production ofA. fructose 6-phosphateB. fructose 1-phosphateC. fructose 1,6-bisphosphateD. pentose 6-phosphate + carbon dioxideE. None of the aboveAns: B31. Phosphorylase is activated most directly byA. epinephrine.B. phosphorylase kinase.C. phosphorylase phosphatase.D. cAMP.E. glucagon.Ans: B32. UDP-glucose is intermediate in each of these conversions EXCEPT which one?A. glucose to glycogenB. fructose to glycogenC. galactose to glycogenD. glycogen to glucoseE. galactose to glucoseAns: D33. Which one of the following molecules is a negative allosteric effector ofphosphofructokinase?A. Succinic acid

B. ADPC. OxaloacetateD. CitrateE. All of the aboveAns: D34. The biosynthesis of glycogen from glucose phosphateA. is catalyzed by glycogen phosphorylase.B. requires UTP.C. is stimulated by a low energy charge.D. occurs in the mitochondrial matrix.E. is stimulated by increased levels of cyclic AMP.Ans: B35. Which is an unlikely metabolic fate of glucose--phosphate in muscle?A. Conversion to fructose-6-phosphate.B. Conversion to glucose-1-phosphate.C. Conversion to dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.D. Hydrolysis to glucose.E. Conversion to lactate.Ans: D36. Binding of epinephrine to muscle cell receptors results directly in increased activityofA. glycogen synthase.B. phosphofructokinase.C. isocitrate dehydrogenase.D. glucose 6-phosphatase.E. adenyl cyclase.Ans: E37. The activity of which enzyme is controlled by phosphorylation anddephosphorylation of serine residues?A. glucokinaseB. PEP carboxykinaseC. phosphofructokinaseD. 3-phosphoglyceraldehyde dehydrogenaseE. glycogen phosphorylaseAns: E38. Which statement concerning phosphorylase is FALSE?

A. The active enzyme catalyzes the reaction: (glucose)n + Pi -> (glucose)n-1 + Glucose-1-PB. The enzyme is activated by phosphorylation.C. Phosphorylation of phosphorylase in muscle is controlled by glucagon.D. The phosphorylation of phosphorylase is catalyzed by a protein kinase.E. The phosphorylation of phosphorylase increases at higher concentrations of cAMPAns: C39. The effects of insulin on glucose uptake by muscle tissue are most directly opposedbyA. cortisol.B. glucagon.C. epinephrine.D. somatomedin A.E. thyroid hormones.Ans: B40. Which enzyme uses inorganic phosphate as a substrate?A. glucose 6-phosphatase.B. phosphofructokinase.C. glucokinase.D. glucose 6-phosphate dehydrogenase.E. glyceraldehyde 3-phosphate dehydrogenase.Ans: E41. The principal tissue involved in gluconeogenesis to provide glucose for theresynthesis of muscle glycogen following prolonged exercise isA. skeletal muscle.B. brain.C. kidney.D. heart muscle.E. liver.Ans: E42. The glycogen branching enzyme is classified asA. a glycogen phosphorylase.B. a uridine diphosphate glucose-glycogen glucosyl transferase.C. an amylo (1,4 --> 1,6)D. a beta-amylase.E. an alpha-amylase.Ans: C

43. Glucagon plays a homeostatic role byA. being released from the pancreas in response to elevated blood glucose levels andthen activating the liver phosphorylase system.B. being released from the pancreas in response to lowered blood glucose levels and thenactivating the liver phosphorylase system.C. stimulating the release of glucose residues from muscle glycogen during periods ofintense muscular activity.D. activating adenylate cyclase in skeletal muscle cells.E. facilitating glucose uptake into skeletal muscle.Ans: B44. Glycolysis will cease ifA. the concentration of cAMP is decreased.B. phosphofructokinase is activated.C. mitochondria are not present in the cell.D. NADH is not oxidized.Ans: D45. The actions of glycogen phosphorylase and the debranching enzyme on glycogenresults in which of the following product or products?A. glucose 6-phosphateB. glucose 1-phosphate and glucoseC. UDP-glucoseD. glucose 6-phosphate and glucoseE. UDP-glucose and glucoseAns: B46. In glycogen, what types of linkages are present between the glucose units?A. Beta-1,4-linkages onlyB. Beta-1,4 and beta-1,6 linkagesC. Alpha-1,4 linkages onlyD. Alpha-1,4 and alpha-1,6 linkagesE. Beta-1,3 linkagesAns: D47. Which liver enzyme is required to form glucose from both glycogen and lactate?A. pyruvate carboxylaseB. fructose-1, 6-bisphosphataseC. glucose-6-phosphataseD. phosphorylase aE. phosphoglucomutase

Ans: C48. Which of the following are activators of glycolysis AND inhibitors ofgluconeogenesis? 1. AMP 2. ATP 3.citrate 4..fructose 2,6-bisphosphate 5. fructose 1,6-bisphosphateA. 1 and 3B. 2 and 4C. 3 and 5D. 4 and 1E. 5 and 3Ans: D49. Which of the following enzymes forms alpha-, linkages in glycogen?A. glycogen synthaseB. glycogen branching enzymeC. amylo-(1,6)D. phosphorylase kinaseAns: B50. For which glycolytic enzyme is inorganic phosphate a substrate?A. aldolaseB. glucose-6-phosphataseC. enolaseD. glyceraldehyde-3-phosphate dehydrogenaseE. pyruvate kinaseAns: D51. The disaccharide lactose is composed ofA. galactose and mannose.B. glucose and mannose.C. glucose and galactose.D. glucose and glucosamine.E. glucose and fructose.Ans: C52. Which of the following enzymes reactivates inactive liver phosphorylase?A. glycogen synthaseB. glycogen branching enzymeC. amylo-(1,6)D. phosphorylase kinase

Ans: D53. Glycogen phosphorylase P (the phosphorylated form) may be activated byA. ATP.B. AMP.C. glucose-1-phosphate.D. glucose-6-phosphate.E. fructose-1,6-biphosphate.Ans: D54. The following enzyme(s) is/are required to synthesize phosphoenol_pyruvate frompyruvate in gluconeogenesis:A. pyruvate kinaseB. pyruvate carboxylase and phosphoenolpyruvate carboxykinaseC. Fructose-1,6-bisphosphatase and glucose-6-phosphataseD. pyruvate dehydrogenaseE. phosphoenolpyruvate dehydrogenase and pyruvate alpha_ketolaseAns: B55. A decrease in the ATP:ADP ratio would result inA. a decrease in phosphofructokinase activity.B. a decrease in the rate of electron transport and oxidative phosphorylation.C. an increase in the net flux of intermediates through the glycolytic pathway.D. a decrease of isocitrate dehydrogenase activity.E. none of the aboveAns: C56. Which statement about gluconeogenesis is correct?A. The acetate group of acetyl-CoA is used for the net synthesis of glucose.B. It occurs primarily in skeletal muscle.C. It occur through reversal of the reactions of glycolysis.D. Lactate and alanine can both serve as substrates.E. ATP is not required.Ans: D57. For gluconeogenesisA. The enzymes that catalyze the 3 irreversible steps of glycolysis are used in theprocess of glucose synthesis.B. The enzymatic reactions are carried out in 3 different subcellular compartments.C. The brain and testis are the most important tissues involved.D. No high energy phosphate compounds are involved.

Ans: B58. Which is a positive allosteric effector of phosphofructokinase?A. glucose 6-phosphateB. acetyl-CoAC. citrateD. fructose 2,6-bisphosphateE. ATPAns: D59. Two enzymes specifically required for gluconeogenesis from lactate but not fromglycerol areA. pyruvate kinase and phosphoglycerate kinase.B. pyruvate carboxylase and phosphoenolpyruvate carboxykinase.C. glucose 6-phosphate dehydrogenase and phosphoenolpyruvate carboxykinase.D. fructose 1,6-bisphosphatase and phosphofructokinase-1.E. glyceraldehyde 3-phosphate dehydrogenase and aldolase.Ans: B60. Biotin participates in the reaction catalyzed byA. phosphoenolpyruvate carboxylase kinase.B. pyruvate carboxylaseC. pyruvate dehydrogenase.D. pyruvate kinase.E. lactate dehydrogenase.Ans: B61. InsulinA. stimulates the phosphodiesterase enzyme which breaks down cAMP.B. decreases the concentration of fructose-2,6-bisphosphate in liver.C. inhibits hepatic glycolysis.D. stimulates glucose transport into the liver.E. has the same effect on glycolysis in the liver as glucagon.Ans: A62. All the following statements about the enzyme glyceraldehyde -phosphatedehydrogenase are correct EXCEPTA. it conserves the energy of an oxidation reaction as a high energy phosphate bond.B. the enzyme forms a covalent high energy intermediate in the reaction.C. NAD is required for the enzyme to function.D. ATP is a product of the reaction.E. phosphate is consumed in the reaction.

Ans: D63. A substrate which transfers phosphate directly to ADP isA. 3-phosphoglycerate.B. 3-phosphoglyceraldehyde.C. phosphoenolpyruvate.D. fructose 1,6-bisphosphate.E. 2-phosphoglyceric acid.Ans: C64. All of the following statements about galactose and its metabolism are true EXCEPT:A. A UDP-glucose molecule is an intermediate in galactose metabolism.B. Galactokinase uses ATP as substrate.C. Galactose is a ketose.D. Galactose is converted to glucose in the liver.E. Digestion and absorption of lactose results in an increase in blood glucoseconcentrations.Ans: C65. Cyclic AMPA. has a phosphodiester bond between C-5 and C-2 carbons of the ribose moiety.B. inhibits glucose-6-phosphatase.C. is degraded in response to high glucagon levels.D. is synthesized directly from AMP.E. modulates the level of fructose 2,6 bisphosphate.Ans: E66. Glycolysis is only partially reversible because of energy barriers at the reactionscatalyzed byA. hexokinase, triose phosphate isomerase, and pyruvate kinase.B. phosphofructokinase, aldolase, and lactate dehydrogenase.C. hexokinase, pyruvate dehydrogenase, and phosphoenolpyruvate carboxykinase.D. hexokinase, phosphofructokinase, and pyruvate kinase.E. hexokinase, glyceraldehyde 3-phosphate dehydrogenase, pyruvate kinase.Ans: D67. An increase in glucagon will causeA. an increase in liver glycogenolysis.B. a decrease in blood glucose.C. an inactivation of liver adenyl cyclase.D. an increase in muscle glycogenesis.

Ans: A68. The enzyme that catalyzes the conversion of fructose-l,-bisphosphate to fructose--phosphate + Pi is classified asA. an oxidoreductase.B. a transferase.C. a hydrolase.D. a lyase.E. a ligase.Ans: C69. All of the following metabolic conditions favor the conversion of pyruvate to glucoseEXCEPTA. an active form of pyruvate carboxylase.B. a rapid rate of fatty acid oxidation.C. an energy charge near 1.0.D. a low level of active phosphoenolpyruvate carboxykinase.E. an inhibited pyruvate dehydrogenase complex.Ans: D70. If liver glucose -phosphatase were deficient, what would best characterize theexpected change in metabolism relative to the normal state?A. increased energy supply to the brain.B. hyperglycemia after a normal meal.C. depletion of glycogen stores in liver.D. hypoglycemia one or two hours after a meal.Ans: D71. Glucocorticoids such as cortisol and corticosterone have distinct effects on hepaticcarbohydrate metabolism, such as promoting gluconeogenesis and glycogen deposition.The likely mechanism of these effects involvesA. binding of glucocorticoids to liver cell membrane receptors with concomitantactivation of adenylate cyclase.B. acute stimulation of enzymes in the pathways of gluconeogenesis and glycogenesis.C. direct inhibition of enzymes participating in glycolysis and glycogenesis.D. induction of new enzyme synthesis for enzymes in the pathways of gluconeogenesisand glycogen synthesis.Ans: D72. Which of the following is an enzyme which catalyzes a freely reversible reactionunder physiological conditions?

A. glucose 6-phosphataseB. phosphofructokinaseC. aldolaseD. phosphoenolpyruvate carboxykinaseE. fructose bisphosphataseAns: C73. In the following pathway for conversion of glucose to pyruvate, what is compoundX? glucose --> --> --> --> glyceraldehyde -phosphate --> X --> phosphoglycerate --> --> --> pyruvateA. glyceraldehyde 2- phosphateB. 2-phosphoglycerateC. 1,3-bisphosphoglycerateD. 1-phosphoglycerateE. 2,3-bisphosphoglycerateAns: C74. All of the following statements concerning the conversion of pyruvate to glucose inmammals are true EXCEPTA. electrons are shuttled from mitochondria to the cytoplasm during this conversion.B. high levels of cellular ATP results in stimulation of this process.C. GTP is involved in this process.D. only one regulated enzyme is involved in the overall conversion of pyruvate toglucose.E. some of the enzymes of glycolysis participate in the conversion.Ans: D75. Adenylate cyclase is an enzyme which increases the concentration of the secondmessenger, cyclic AMP. In liver high adenylate cyclase activity brings aboutA. conversion of glycogen synthase D to glycogen synthase I.B. increased conversion of carbohydrate into fatty acids.C. increased conversion of phosphorylase a to phosphorylase b.D. increased lipogenesis from gluconeogenic amino acids.E. increased activity of a protein kinase.Ans: E76. During the breakdown of glycogen, free glucose is formed fromA. the reducing end.B. the non-reducing end.C. glucose residues in an alpha 1-->4 linkage to the chain.D. glucose residues in an alpha 1-->6 linkage to the chain.E. hydrolysis of glucose 1-phosphate.

Ans: D77. All of the following can stimulate the activity of muscle glycogen phosphorylaseEXCEPTA. calcium ions.B. epinephrine.C. cyclic AMP.D. phosphorylase kinase.E. glucagon.Ans: E78. What is the primary process by which epinephrine increases blood sugar?A. synthesis of carbohydrate from fatB. absorption of carbohydrate from the digestive tractC. liver glycogenesisD. liver glycogenolysisE. glyconeogenesisAns: D79. Which reaction is catalyzed by glycogen synthase?A. UTP + glucose 1-P --> UDP-glucose + PPiB. UDP glucose + glycogenin --> PPi + glycogenn+1C. UDP glucose + glycogenin --> UMP + Pi + glycogenn+1D. glycogenin + UDP-glucose --> glycogenn+1 + UDPE. glucose 6-P + glycogenin --> Pi + glycogenn+1Ans: D80. The glycerol phosphate shuttleA. results in production of dihydroxyacetone phosphate in the matrix of mitochondria.B. transfers electrons from cytosolic NADH to the respiratory chain of mitochondria.C. inhibits glycolysis.D. supports phosphorylation of three moles of ADP per mole of cytosolic NADHoxidized.E. uses 3-phosphoglyceric acid as a substrate.Ans: B81. All of the following statements concerning gluconeogenesis are correct EXCEPTwhich one?A. gluconeogenesis from lactate occurs in both mammalian liver and muscle.B. One mole of glucose is produced from two moles of lactate.C. Given ATP, all the reactions of gluconeogenesis can occur in the absence of air.

D. Although a net of two molecules of ATP are generated per molecule of glucoseconverted to lactate, six molecules of ATP (or its equivalent) are required to synthesizeone molecule of glucose from lactate.E. Photosynthesis in green plants utilizes part of the gluconeogenic pathway for hexosesynthesis.Ans: A82. Which statement about glycolysis is TRUE?A. The first step for which ATP is required is catalyzed by phosphofructokinase.B. The rate of glycolysis in the absence of oxygen is usually less than the rate in thepresence of oxygen.C. The phosphoglycerate kinase reaction is reversible under physiological conditionsbut the hexokinase reaction is not.D. The product of the reaction catalyzed by triose phosphate isomerase isphosphoenolpyruvate.E. The conversion of pyruvate to lactate requires NAD.Ans: C83. The action of phosphoprotein phosphatase would be expected to activate which of thefollowing?A. phosphorylaseB. glycogen synthaseC. protein phosphatase inhibitor_1D. phosphorylase kinaseE. cAMP_dependent protein kinaseAns: B84. Which of the following compounds is the direct glucosyl donor in the biosynthesis ofglycogen in animal tissue?A. uridine diphosphate glucoseB. thymidine diphosphate glucoseC. glucose 1-phosphateD. adenosine diphosphate glucoseE. glucose 1,6-bisphosphateAns: A85. Muscle cells are metabolizing glucose in the absence of oxygen. What change willoccur when oxygen is introduced?A. increased rate of utilization of glucoseB. decreased rate of utilization of glucoseC. increased accumulation of lactateD. activation of phosphofructokinase

E. decreased activity of the Krebs cycleAns: B86. The action of the enzyme phosphorylase kinase results in theA. activation of glycogen synthase.B. inactivation of glycogen synthase.C. activation of glycogen phosphorylase.D. inactivation of glycogen phosphorylase.E. activation of a protein phosphatase.Ans: C87. A rise in ATP/ADP ratio in liver tends to increase theA. degradation of glycogen.B. glycolysis activity.C. activity of phosphofructokinase.D. activity of gluconeogenesis.E. concentration of AMP.Ans: D88. Regulated steps in glycolysis of muscle tissue include which of the following? () thephosphohexose isomerase reaction () the phosphofructokinase reaction () the enolasereaction () the phosphoglycerate kinase reaction () the pyruvate kinaseA. 1 and 3B. 2 and 4C. 3 and 5D. 1 and 4E. 2 and 5Ans: E89. The two enzymes which catalyze the substrate-level phosphorylation of ADP to ATPin glycolysis areA. hexokinase and glycerol kinase.B. succinyl-CoA synthase and phosphorylase b kinase.C. phosphofructokinase and pyruvate kinase.D. pyruvate kinase and 3-phosphoglycerate kinase.E. phosphoenolpyruvate carboxykinase and 3-phosphoglycerate kinaseAns: D90. Galactose is found in the hydrolytic products of:A. maltose.B. amylose.

C. lactose.D. sucrose.E. glycogen.Ans: C91. All of the following statements concerning glycogen synthase are true EXCEPTwhich one?A. The D and I forms of the enzyme are interconvertible through phosphorylation anddephosphorylation.B. The D form depends upon high intracellular levels of glucose 6-phosphate in order tobe active.C. In skeletal muscle, increased intracellular levels of glycogen inhibits the conversionof the D form to the I form.D. High intracellular levels of ATP can stimulate glycogen synthase D activity.E. None of the above; they are all true.Ans: D92. Enzymes in liver which are exclusively gluconeogenic areA. glucose 6-phosphatase, fructose 1,6-bisphosphatase and glucokinase.B. PEP carboxykinase, glucose 6-phosphatase and aldolase A.C. fructose bisphosphatase, pyruvate dehydrogenase and PEP carboxykinase.D. PEP carboxykinase, fructose bisphosphatase and glucose 6-phosphatase.Ans: D93. Glycogen synthaseA. catalyzes a freely reversible reaction.B. catalyzes the synthesis of alpha-1,6 glycosidic linkages.C. requires a primer.D. uses glucose 1-phosphate as a substrate.E. when phosphorylated yields a more active form.Ans: C94. Which of the following type of cells are not dependent on insulin for glucosetransport?A. Skeletal muscleB. Adipose tissueC. KidneyD. BrainE. C & DAns: E

95. Which directly stimulates the activity of glycogen synthase D?A. AMPB. glucose 6-phosphateC. ATPD. epinephrineE. cAMPAns: B96. Which of the following statements concerning the regulation of glycolysis andgluconeogenesis is FALSE?A. Citrate inhibits gluconeogenesis.B. Fructose-2,6-bisphosphate stimulates glycolysis.C. insulin stimulates glycolysis.D. NADH and acetyl-CoA inhibit the formation of more acetyl-CoA.E. glucagon inhibits glycolysis in the liver but not in skeletal muscle.Ans: A97. Which of the following statements best describes the mechanism for glucagon'scontrol of metabolism?A. glucagon allosterically regulates many enzymes directly.B. glucagon decreases the synthesis of glycolytic enzymes.C. glucagon stimulates a cAMP mediated cascade which results in the phosphorylationof one or more target enzymes.D. glucagon decreases membrane permeability to glucose.E. glucagon decreases membrane permeability to fatty acids.Ans: C98. Which is NOT an obligatory intermediate in the anaerobic glycolysis of glucose?A. glucose 6-phosphateB. glucose 1-phosphateC. fructose 6-phosphateD. fructose 1,6-bisphosphateE. 3-phosphoglyceraldehydeAns: B99. The main organ responsible for keeping the blood glucose level steady between mealsby making glucose via gluconeogenesis is theA. pancreas.B. kidney.C. liver.D. muscles.E. adipose tissue.

Ans: C100. Glucagon secretion would be most likely to lead to the elevation of which one of thefollowing enzymes?A. acetyl CoA carboxylaseB. citrate lyaseC. phosphoenolpyruvate carboxykinaseD. 3-hydroxy-3-methyl glutaryl CoA reductaseE. lipoprotein lipaseAns: C101. Acetyl-CoA regulates gluconeogenesis by activatingA. phosphoenolpyruvate carboxykinase.B. pyruvate kinase.C. pyruvate carboxylase.D. lactate dehydrogenaseE. fructose 1,6-bisphosphatase.Ans: C102. Sucrose is a disaccharide composed of __ linked to__ .A. galactose, glucoseB. glucose, glucoseC. galactose, fructoseD. fructose, fructoseE. glucose, fructoseAns: E103. Two allosterically regulated enzymes on the pathway from lactate to glucose areA. phosphofructokinase and pyruvate kinaseB. pyruvate carboxylase and fructose 1,6-bisphosphataseC. fructose 1,6-bisphosphatase and glyceraldehyde 3-phosphate dehydrogenaseD. pyruvate dehydrogenase and pyruvate carboxylaseAns: B104. All of the following statements apply to skeletal muscle glycogen phosphorylaseEXCEPT which one?A. Phosphate ion is one substrate of this enzyme.B. Its activity is increased by high levels of AMP.C. The fully functional enzyme has more than one active site.D. The b form contains a phosphorylated serine group.E. The activity of the liver enzyme is influenced by levels of epinephrine.

Ans: D105. An enzyme required for gluconeogenesis and which uses GTP as a substrate isA. pyruvate dehydrogenaseB. pyruvate carboxylaseC. malate dehydrogenaseD. pyruvate kinaseE. phosphoenolpyruvate carboxykinaseAns: E106. In the carboxylation of pyruvate to oxaloacetate by the enzyme pyruvatecarboxylase, acetyl CoA interacts with pyruvate carboxylase as aA. substrate.B. noncompetitive inhibitor.C. homotropic activator.D. heterotropic activator.E. competitive inhibitor.Ans: D107. All of the following would be caused by or would be the result of increased levels ofepinephrine in the circulatory system EXCEPTA. production of cyclic-AMP.B. activation of a protein kinase.C. phosphorylation in liver cells of side-chain of specific serine units of certain proteins.D. stimulation of a phosphoprotein phosphatase.E. increased breakdown of liver glycogen.Ans: D108. Fructose ,-bisphosphate stimulatesA. fructose 1,6-bisphosphataseB. fructose 6-phosphateC. glucokinaseD. phosphofructokinase-1Ans: D109. The earliest consequence of an increase in the level of cyclic AMP in muscle cellswill beA. stimulation of adenylate cyclase.B. inhibition of phosphodiesterase.C. dissociation of the catalytic subunit of protein kinase from the regulatory subunit.D. phosphorylation of phosphorylase b kinase.

E. increased rate of glycogen breakdown.Ans: C110. The conversion of UDP-galactose to UDP-glucose involvesA. an isomerase.B. a mutase.C. an epimerase.D. an aldolase.E. a dehydrase.Ans: C111. Enzymes catalyzing reactions that are essentially irreversible under physiologicalconditions includeA. phosphopentose isomerase.B. hexokinase.C. aldolase.D. phosphoglycerate kinase.E. more than one of the above.Ans: B112. Which of the following would stimulate the principal controlled step of glycolysis?A. ATPB. citrateC. fructose 2,6_bisphosphateD. glucose 6_phosphateE. fructose 1,6_bisphosphateAns: C113. Concerning the reaction Phosphoenolpyruvate + ADP -----> pyruvate + ATP whichof the following statements is true?A. Formation of ATP and pyruvate occurs since under intracellular conditions thehydrolysis of ATP is exergonic while the hydrolysis of phosphoenolpyruvate isendergonic.B. Reaction is an example of oxidative phosphorylation.C. Reaction equilibrium lies far to the left.D. Formation of ATP and pyruvate occurs since hydrolysis of phosphoenolpyruvateresults in the release of free energy that is numerically larger than the free energyassociated with the phosphorylation of ADPE. None of the above is correct.Ans: D

114. What is the approximate yield of ATP (from ADP) when one residue of glucose,released from glycogen, is converted to lactic acid under anaerobic conditions?A. 0B. 1C. 2D. 3E. 4Ans: D115. Glycogen in muscleA. serves as a source of fuel for ATP synthesis within that tissue.B. serves primarily as a buffer of blood glucose levels.C. serves as a source of glucose-6-phosphate which is subsequently dephosphorylated byglucose-6-phosphatase and transported out of the cell.D. is rapidly depleted during fasting.Ans: A116. All of the following are gluconeogenic enzymes EXCEPTA. glucose 6-phosphatase.B. fructose 1,6-bisphosphatase.C. phosphoenolpyruvate (PEP)-carboxykinase.D. pyruvate carboxylase.E. pyruvate dehydrogenase.Ans: E117. Which characterizes the activity of (glycogen) debranching enzyme?A. breakage of alpha-1,4-bondsB. breakage of alpha-1,6-bondsC. transfer of a chain of three glucosyl residues.D. production of free glucoseE. all of the aboveAns: E118. Using a signal transduction pathway, glucagon influences the activity of the enzymethat catalyses the formation ofA. fructose 1_phosphate.B. fructose 6_phosphate.C. fructose 1,6_bisphosphate.D. fructose 2_phosphate.E. fructose 2,6_bisphosphate.Ans: E

119. The NET products of anaerobic glycolysis areA. pyruvate, NAD, ATP.B. lactate, NAD, ATP.C. lactate, ATP.D. acetyl-CoA, NADH, ATP.E. pyruvate, ATP.Ans: C120. The formation of one molecule of glucose from pyruvate in liver requires assubstratesA. one molecule each of GTP and ATP.B. two molecules each of GTP and ATP.C. two molecules of GTP and four molecules of ATP.D. two molecules of GTP and eight molecules of ATP.E. one molecule of GTP and two molecules of ATP.Ans: C121. An enzyme required for gluconeogenesis from lactate and which uses ATP as asubstrate isA. pyruvate dehydrogenase.B. pyruvate carboxylase.C. malate dehydrogenaseD. phosphoenolpyruvate carboxykinase.E. pyruvate kinase.Ans: B122. Fructose-,-bisphosphateA. allosterically inhibits hepatic gluconeogenesis.B. phosphorylates 6-phosphofructo-1-kinase.C. is elevated in pyruvate kinase deficiency.D. uncouples oxidative phosphorylation.E. modulates oxygen binding by hemoglobin.Ans: A123. When glycogen synthase is phosphorylated, itA. is inactive but can be allosterically stimulated by AMP.B. is active in the synthesis of glycogen from UDP-glucose.C. catalyzes synthesis of alpha-1,6 bonds between glucose molecules.D. is inactive but can be allosterically stimulated by glucose 6-phosphate.E. acquires a phosphate group on a tyrosine residue.

Ans: D124. Phosphorylase aA. contains phosphorylated serine residues.B. exists as a dimer.C. is the less active form of the enzyme.D. is activated directly by cyclic AMP.E. none of the aboveAns: A125. The hepatic sensor of blood glucose levels is:A. Adenylate cyclaseB. CalmodulinC. Fructose bisphosphataseD. phosphofructokinaseE. Phosphorylase bAns: E126. Ethanol may inhibit gluconeogenesis byA. direct activation of glucose 6-phosphatase.B. competition with lactate for NAD.C. inhibition of pyruvate dehydrogenase.D. inhibition of fatty acid oxidation.E. decreasing FAD in liver.Ans: B127. Which of the following participates in sugar transfer reactions in man?A. UDP-beta-D-glucoseB. UDP-alpha-D-glucoseC. GDP-beta-D-mannoseD. UDP-alpha-D-mannoseE. GDP-alpha-D-galactoseAns: B128. High concentrations of glucosephosphateA. stimulate hexokinase.B. stimulate glucokinase.C. stimulate phosphorylase.D. stimulate glycogen synthase D.E. inhibit phosphofructokinase-1.

129. The immediate event that occurs to glucose on entering a liver cell that prevents theglucose from escaping the cell isA. conversion into galactose.B. phosphorylation at C-6.C. phosphorylation at C-1.D. polymerization into glycogen.E. oxidation at C-6.Ans: B130. Gluconeogenesis is stimulated byA. glucagon and norepinephrine.B. epinephrine and somatostatin.C. glucagon and epinephrine.D. insulin and glucagon.Ans: C131. Which of the following stimulates gluconeogenesis?A. high concentration of acetyl CoA in the mitochondriaB. high concentration of fatty acyl CoA in the cytosolC. insulinD. high concentration of fructose-2,6-bisphosphate in the cytosolE. increase in the amount of the enzyme glucokinaseAns: A132. Mannose is made in the body from glucose. The immediate precursor of mannose -phosphate isA. glucose 6-phosphate.B. UDP-mannose.C. fructose 6-phosphate.D. mannose 1-phosphate.E. fructose 1-phosphate.Ans: C133. AMP (cyclic AMP) activates glycogen phosphorylase by which mechanism?A. It adenylates inactive phosphorylase converting it to an active form.B. It allosterically activates the phosphorylase.C. It allosterically inhibits phosphorylase phosphatase.D. It allosterically activates an enzyme which initiates a series of reactions resulting inthe activation of phosphorylase.E. It phosphorylates an enzyme which initiates a series of reactions resulting in theactivation of phosphorylase.

Ans: D134. All of the following mechanisms govern the activity of phosphofructo- kinase-(PFK-) EXCEPTA. Fructose 1,6-bisphosphate stimulates PFK-1.B. ATP inhibits PFK-1.C. Fructose 2,6-bisphosphate stimulates PFK-1.D. AMP stimulates PFK-1.E. Citrate inhibits PFK-1.Ans: A135. The Cori cycle is important as a consequence of the lack of which of the followingenzymes in muscle?A. enolaseB. aldolaseC. fructose 1,6-bisphosphataseD. glucokinaseE. glucose 6-phosphataseAns: E136. The increase in blood sugar level resulting from epinephrine injection can best beexplained by which one of the following?A. Synthesis of carbohydrate from fatB. Absorption of carbohydrate from the digestive tractC. Liver glycogenesisD. Liver glycogenolysisE. gluconeogenesisAns: D137. There cannot be significant net formation of glucose from stearic acid in a mammalbecause of the irreversibility of the reaction catalyzed byA. pyruvate kinase.B. pyruvate carboxylase.C. hexokinase.D. pyruvate dehydrogenase.E. glucose 6-phosphate dehydrogenase.Ans: D138. The most important enzyme in the physiological regulation of glycolysis isA. hexokinase.B. hexosephosphate isomerase.C. phosphofructokinase.

D. triose phosphate isomerase.E. aldolase.Ans: C139. Which statement is true of glucokinase?A. It catalyzes the phosphorylation of fructose.B. It has a lower Km for glucose than does hexokinase.C. It is found in liver.D. It does not require Mg++.E. None of the above is correct.Ans: C140. Glucuronic acid is synthesized most directly fromA. ascorbic acid.B. gluconolactone.C. UDP-glucose.D. galactose.E. glucose.Ans: C141. You have just been awarded a grant to study the relationship of glycogenmetabolism to blood glucose levels in laboratory rats and are planning your firstexperiments. Which of the following tissues would be the most critical to include in yourstudy?A. Adipose tissueB. LiverC. Skeletal muscleD. KidneyE. Bone marrowAns: B142. Phosphofructokinase catalyzes the phosphorylation of fructose -phosphate to formfructose ,-bisphosphate. ATP is the phosphate donor and also inhibitsphosphofructokinase. How can ATP act as a substrate and as a feedback inhibitor?A. The formation of fructose 1,6-bisphosphate is forced toward completion becausestandard free energy for the reaction is negative.B. There are two ATP-binding sites on the enzyme; a catalytic site with low affinity anda regulatory binding site with high affinity. At high ATP levels, the enzyme is inhibitedfully.C. There are two ATP-binding sites on the enzyme; a catalytic site with a high affinityfor ATP, and a regulatory site with low ATP affinity. The enzyme is shut down only athigh ATP concentrations when the energy charge is high.

D. There is a single ATP-binding site; binding ATP lowers the probability of reaction fora short time, even after ATP is unbound. Thus a high ATP concentration inhibits thereaction.E. none of the aboveAns: C143. One form of glycogen synthase has a requirement for glucose -phosphate (GP). Thisis becauseA. G6P is a feedback inhibitor of the enzyme.B. G6P is required for activation of the enzyme by cAMP.C. G6P is a substrate for the enzyme.D. G6P is an allosteric activator of glycogen synthase.E. G6P is a substrate for branching enzyme.Ans: D144. Net gluconeogenesis (the net synthesis of glucose) can be carried out using which ofthe following metabolic intermediates as a starting material? . acetyl CoA . oxaloacetate .acetoacetate . pyruvate . stearic acidA. 1 and 3B. 2 and 4C. 3 and 5D. 4 and 5E. 2 and 3Ans: B145. Oxidation of NADH produced in the cytoplasm can be catalyzed by all EXCEPTA. lactate dehydrogenase.B. alpha-glycerol phosphate dehydrogenase.C. cytoplasmic malate dehydrogenase.D. 3-Phosphoglyceraldehyde dehydrogenase.E. glucose 6-phosphate dehydrogenase.Ans: E146. When epinephrine binds to its receptor on skeletal muscle, glycogenolysis isstimulated. The hormone signal influences the activity of each of these enzymesEXCEPTA. phosphorylase.B. adenylate cyclase.C. phosphorylase kinase a.D. cyclic AMP-dependent protein kinase.E. debranching enzyme.

Ans: E147. You are studying a patient with an unusual metabolic defect resulting in abnormalglucose metabolism. You have determined that the patient has very low levels ofphosphofructokinase_ and fructose ,_bisphosphate. Which of the following would youpredict?A. increased rate of glycolysisB. decreased rate of gluconeogenesis and increased rate of glycolysisC. decreased rate of glycolysis and increased rate of gluconeogenesisD. decreased rate of gluconeogenesisAns: C148. All of the following are negative modulators of liver pyruvate kinase EXCEPTA. alanine.B. fructose 1,6-bisphosphate.C. palmitic acid.D. oleic acid.E. ATP.Ans: B149. How many moles of ATP (or equivalent) are required for the reactions throughwhich lactic acid is converted to a mole of glucose in the liver.A. 2.B. 3.C. 4.D. 5.E. 6.Ans: E150. Which of the following tissues utilize insulin_dependent (GLUT) transporters forglucose uptake?A. Brain, muscle, small intestineB. Adipose, skeletal muscle, heart muscleC. Liver, cardiac muscle, pancreasD. Skeletal muscle, connective tissue, nervous tissueAns: B151. The reaction that is common to both the breakdown and the biosynthesis of glucoseisA. glucose + ATP < ---> glucose-6-phosphate + ADP.B. fructose 6-phosphate + ATP fructose 1,6-bisphosphate + ADP.C. phosphoenolpyruvate + ADP pyruvate + ATP.

D. 1,3-bisphosphoglycerate + ADP 3-phosphoglycerate + ATP.E. glucose 6-phosphate + water glucose + Pi.Ans: D152. During gluconeogenesis, which enzyme must be present in addition to the glycolyticenzymes?A. fructose 1,6-bisphosphate phosphataseB. phosphofructokinaseC. pyruvate kinaseD. pyruvate dehydrogenaseE. glyceraldehyde 3-phosphate dehydrogenaseAns: A153. The reducing equivalents of cytosolic NADH derived from glycolysis can beutilized for the mitochondrial electron transport system byA. Direct donation of electrons to cytochrome c in the intermembrane space.B. Transport of NADH into the mitochondrial matrix and donation of electrons toelectron transport complex I.C. Reduction of dihydroxyacetone phosphate to phosphatidyl glycerol, transport ofphosphatidyl glycerol into the mitochondrial matrix, reduction of NAD+ to NADH, anddonation of electrons to complex I.D. Direct reduction of FAD by NADH by mitochondrial glycerol_3_ phosphatedehydrogenase.E. Reduction of cytosolic oxaloacetate to malate, transport of malate into themitochondrial matrix, reoxidation of malate to oxaloacetate and reduction of NAD+ toNADH, and donation of electrons from NADH to complex I.Ans: E154. An enzyme in the glycolytic pathway that results in the conversion of hexose-bisphosphate into triose-phosphates isA. hexokinase.B. triose isomerase.C. aldolase.D. pyruvate kinase.E. citrate synthase.Ans: C155. Which pair of enzymes participates in the synthesis of glycogen from glucose?A. glycogen phosphorylase and amylo-1,6-glucosidaseB. phosphoglucomutase and UDP-glucose pyrophosphorylaseC. glycogen synthase and glycogen phosphorylaseD. amylase and amylo-1,6-glucosidase

E. glucose 6-phosphatase and phosphoglucose isomeraseAns: B156. As blood levels of glucagon increase, there is a concomitantA. decrease in liver glycogenolysis.B. decrease in blood glucose.C. activation of liver adenylate cyclase.D. increase in muscle glycogenesis.E. increase in fructose 2,6_bisphosphate.Ans: C157. FructoseA. unlike glucose, cannot be metabolized by any part of the glycolytic pathway.B. in the liver, enters directly into glycolysis mainly as fructose-6-phosphate.C. must be isomerized into glucose-6-phosphate before it can be metabolized.D. is converted into UDP-fructose and then epimerized into UDP-glucose.E. catabolism in liver requires the action of a special aldolase that recognizes fructose-1-phosphate.Ans: E158. Which enzyme would be expected to increase in activity on administration ofinsulin?A. fructose 1,6-bisphosphate phosphataseB. pyruvate carboxylaseC. glucokinaseD. glycogen phosphorylaseE. PEP carboxykinaseAns: C159. What is the net yield of NADH when glucose -6-phosphate is converted to lactate byanaerobic glycolysis?A. 0B. 1C. 2D. 3E. 4Ans: A160. Insulin promotes glycogen synthesis in the liver by:A. inhibiting glycogen synthase.B. binding to phosphorylase.

C. causing the dephosphorylation of both phosphorylase and glycogen synthase.D. activating phosphorylase.E. facilitating the transport of glucose into the cell.Ans: C

Chapter 18 Lipid Metabolism II: Pathways of Metabolism of Special Lipids

Multiple Choice

1. Which of the following statements concerning the serum lipoproteins is true?A. The chylomicron particle is smaller than the LDL particle.B. The density of a lipoprotein increases as the ratio of lipid to protein in the particleincreases.C. Most of the triglyceride in serum is contained in VLDL and chylomicrons.D. Most of the cholesterol in serum is contained in LDL as unesterified cholesterol.E. none of the above.Ans: C2. Which of the following is the most correct sequence involved in the synthesis oftriacylglycerols (triglycerides) in the fat cell?A. glycerol 3-phosphate ==> PA ==> 1,2-DG ==> TGB. PA ==> glycerol 3-phosphate ==> 1,2-DG ==> TGC. glycerol 3-phosphate ==> MG ==> DG ==> TGD. glycerol 3-phosphate ==> 1,2-DG ==> PA ==> TGE. glycerol ==> glycerol 3-phosphate ==> PA == 1,2-DG ==> TGAns: A3. Both aspirin and indomethacin block prostaglandin formation by inhibition ofA. cyclooxygenaseB. diacylglycerol lipase.C. 5-lipooxygenase.D. phospholipase A2.E. phospholipase CAns: A4. Which of the following statements about the synthesis of phospholipids is TRUE?A. phosphatidyl ethanolamine is methylated to phosphatidyl choline by S-adenosylmethionine.B. Free unesterified choline reacts with a diglyceride to form phosphatidyl choline.C. phosphatidyl alanine is hydroxylated to form phosphatidyl serine.D. Fatty acids are added to phospholipids as CDP-fatty acids.Ans: A

5. Niemann Pick disease results from a deficiency ofA. lipoprotein lipase.B. sphingomyelinase.C. adipolytic lipase.D. pancreatic lipase.E. none of the above.Ans: B

6. Phosphatidate phosphatase is involved in the synthetic pathway forA. choline.B. glycerol phosphate.C. phosphatidic acid.D. cholesterol.E. triglycerides.Ans: E7. The products of the hydrolysis of sphingomyelin by sphingomyelinase, aphospholipase C - like enzyme, areA. acylceramide and phosphate.B. ceramide and phosphorylcholineC. ceramide, choline, and phosphate.D. ceramide, a fatty acid, and choline.E. ceramide phosphate and choline.Ans: B8. Geranyl pyrophosphate condenses with isopentenyl pyrophosphate to formA. 3,3-dimethylallyl pyrophosphate.B. presqualene pyrophosphate.C. squalene.D. farnesyl pyrophosphate.E. none of the above possibilities.Ans: D9. The uptake of LDL into a cell by the LDL receptor does all of the following EXCEPTA. stimulates cellular acyl-CoA:cholesterol acyltransferase (ACAT).B. inhibits hydroxymethylglutaryl-CoA (HMG-CoA) reductase.

C. decreases the rate of synthesis of the LDL receptor.D. increases cholesterol esterification.E. converts LDL to HDL and HDL remnants.Ans: E10. In the cell, squaleneA. is a hydrocarbon that may undergo attack by oxygen to form an epoxide.B. is a complex fatty acid which accumulates in Refsum's disease.C. is a steroid which is a cholesterol precursor.D. is a product of cholesterol catabolism.E. is found only in sharks of the genus Squalus.Ans: A11. All of the following statements on the biosynthesis of phosphatidylcholine (lecithin)in mammalian adipose tissue are correct EXCEPT which one?A. CTP is requiredB. S-adenosylmethionine is requiredC. The non-phosphorylated form of glycerol phosphate acyl transferase is requiredD. Absence of 3',5'-cyclic AMP is inhibitoryE. phosphatidate phosphohydrolase is requiredAns: E

12. Very low density serum lipoproteins transportA. non-esterified fatty acids to the liver.B. medium chain non-esterified fatty acids via the lymphatic system.C. non-esterified fatty acids to the adipose tissues.D. triacylglycerol from the liver to the adipose tissues.E. none of these.Ans: D13. Capillary lipoprotein lipase is activated byA. Apo B-100.B. Apo C-II.C. Apo C-III.D. Apo A-I.E. Apo E.Ans: B14. Lipoprotein lipase is

A. an intracellular enzyme.B. stimulated by cAMP.C. stimulated by epinephrine.D. stimulated by one of the apolipoproteins found in VLDL.E. the stimulus for mobilization of stored triglycerides from adipose tissue.Ans: D15. All of the following are true about a ceramide EXCEPT which one?A. It has two nonpolar tails.B. The sphingosine base is attached via an amide linkage to a saturated or mono-unsaturated fatty acid.C. The different polar head groups are attached to the hydroxyl group (position 1)of thesphingosine base.D. They are found in highest concentration in depot fat.Ans: D16. A pharmacological dose of a non-steroidal anti-inflammatory agent would not inhibitthe synthesis ofA. thromboxanes.B. prostacyclins.C. leukotrienes.D. E-series prostaglandins.E. F-series prostaglandins.Ans: C17. A characteristic feature common to the degradation of most sphingolipids, includinggangliosides, isA. catalysis by lysosomal enzymes.B. catalysis by peroxisomal enzymes.C. feedback regulation by ceramide.D. hormonal regulation by glucocorticoids.E. participation of nucleotide intermediates.Ans: A

18. In the metabolism of cholesterol in the humanA. cholesterol conversion to bile salts involves shortening of the side chain of cholesterol.

B. plasma cholesterol readily exchanges with the brain cholesterol.C. plasma cholesterol is entirely in the form of cholesterol esters.D. cholesterol can be oxidized to carbon dioxide and water.E. cholesterol is synthesized only in the liver.Ans: A19. In the synthesis of cholesterolA. only the methyl group of acetyl CoA is incorporated.B. most of the reactions take place in the mitochondria.C. dietary cholesterol has no influence on the rate.D. mevalonic acid formation seems to be the controlling step.E. the adrenal gland is the only tissue which is active.Ans: D20. Cholesterol serves as a precursor for each of the following EXCEPTA. prostacyclin.B. pregnenolone.C. glycocholate.D. cholecalciferol (Vitamin D3)Ans: A21. Which group of molecules appropriately combined would form lecithin?A. glucose, N-acetylgalactosamine, glycerol, phosphoric acid, two fatty acidsB. phosphoric acid, glycerol, two fatty acids, cholineC. phosphoric acid, sphingosine, fatty acid, glucose, N-acetylneuraminic acid, N-acetylgalactosamineD. choline, phosphoric acid, sphingosine, fatty acidE. glycerol, two fatty acids, phosphoric acid, ethanolamineAns: B22. The enzyme that condenses serine and palmitoyl-CoA to form -dehydrosphinganinerequiresA. retinal.B. pyridoxal phosphate.C. niacin.D. vitamin B12.E. biotin.Ans: B23. Phosphatidylcholine is synthesized by the reaction ofA. phosphatidic acid and CDP-choline.

B. 1-palmitoyl-sn-glycerol-3-phosphate and CDP-choline.C. 1-palmitoyl-sn-glycerol and CDP-choline.D. lysolecithin and CDP-choline.E. diacylglycerol and CDP-choline.Ans: E

24. Chylomicrons:A. mainly carry dietary triglycerides.B. require the action of LDL for absorption.C. are secreted into the blood directly from the intestine.D. are smaller than HDL.E. have more phospholipid than HDL.Ans: A25. Treatment of phosphatidylcholine with which enzyme would be most likely toliberate arachidonic acid?A. phospholipase A1.B. phospholipase A2.C. phospholipase C.D. phospholipase D.Ans: B26. A precursor of leukotrienes.A. inositol 1,4,5 trisphosphateB. diacylglycerolC. cholera toxinD. arachidonic acidE. cAMPAns: D27. The initial catalytic steps in the synthesis of cholesterol from acetyl-CoA are utilizedby the pathway producingA. acetoacetate.B. ceramide.C. citrate.D. palmitate.

E. ribulose 5-phosphate.Ans: A28. An established function of one of the apolipoproteins in the LDL particle is toA. activate lecithin-cholesterol acyl transferase.B. coat pits in the plasma membrane with its cage-like structure.C. hydrolyze cholesterol esters in preparation for receptor-mediated endocytosis.D. provide a recognition marker for binding to the LDL receptor.E. disrupt the gel network preventing lysosomal budding.Ans: D29. The rate-limiting step in the conversion of cholesterol to bile acids isA. side chain oxidation.B. 12-alpha-hydroxylation.C. 7-alpha-hydroxylation.D. 7-beta-hydroxylation.E. conversion to coprostanol.Ans: C

30. The second step of prostaglandin synthase converts PGG2 to PGH2. What is thecofactor for this reaction?A. BiopterinB. FADH2C. GlutathioneD. NADHE. Pyridoxal phosphateAns: C31. Which of the following is directly involved in the biosynthesis of sphingosine?A. squaleneB. spermineC. serotoninD. serineE. sorbitolAns: D32. Prostaglandins are inactivatedA. primarily in the liver.

B. in the presence of molecular oxygen.C. only in the circulation.D. by oxidation of the 15 hydroxy group by a prostaglandin dehydrogenase.E. by conversion to thromboxanes.Ans: D33. Loss of hexosaminidase A activity results in accumulation ofA. galactocerebroside.B. glucocerebroside.C. G-ganglioside.D. sphingomyelin.E. sulfatideAns: C34. phosphatidylcholine participates in the synthesis of sphingomyelin by providingA. an acylglycerol group.B. a ceramide group.C. a fatty acyl group.D. a phosphorylcholine group.Ans: D35. A ceramide is composed ofA. sphingosine and fatty acid.B. sphingosine and glucose.C. sphingosine and serine.D. glycerol and fatty acid.E. glycerol and choline.Ans: A

36. Which of the following serum lipoproteins possesses the highest concentration ofprotein (mg protein/g lipoprotein)?A. chylomicronsB. VLDLC. IDLD. LDLE. HDLAns: E

37. The principal apoprotein in LDL is:A. apo AI.B. apo B-100.C. apo CII.D. apo B-48.E. apo E.Ans: B38. Transfer of cholesterol from membranes to HDL requiresA. serum albumin.B. lecithin cholesterol acyltransferase.C. cholic acid conjugation.D. lipoprotein lipase.E. partial hydrolysis.Ans: B39. Changes in the extent of phosphorylation of 3-hydroxy-3-methyl glutaryl-CoAreductaseA. are induced by reabsorbed bile acids.B. are regulated by the level of dietary cholesterol.C. control the rate of synthesis of cholesterol.D. represent a type of co-translational modification of the protein.Ans: C40. Cholesterol is metabolized in the mammalian body primarily by conversion toA. vitamins D.B. fatty acids.C. bile acids.D. carbon dioxide.E. mevalonic acid.Ans: C41. CDP-diglyceride is an intermediate in the de novo synthesis ofA. phosphatidylserine.B. phosphatidylcholine.C. phosphatidylethanolamine.D. Triglycerides.E. None of the above.Ans: A

42. In the synthesis of prostaglandins and thromboxanesA. arachidonic acid of the cytosol serves as the primary precursor.B. PG synthase uses 2 molecules of oxygen to generate the endoperoxide PGG2.C. PGE2 synthesis would be inhibited by aspirin but thromboxane synthesis would not beaffected.D. PGH2 is the precursor of PGE2 but PGI2 is the precursor of TXA2.E. all tissues have the capacity to synthesize all of the prostaglandins.Ans: B43. All the following statements regarding ethanolamine are correct EXCEPTA. For the formation of phosphatidyl ethanolamine, ethanolamine needs to be activatedby ATP and CTP.B. Ethanolamine can be produced from serine in the form of phosphatidyl serine.C. Ethanolamine, in the form of phosphatidyl ethanolamine, can be converted tophosphatidyl choline.D. Ethanolamine can exchange reversibly with the serine of phosphatidyl serine.E. The carbons of ethanolamine cannot be derived from glucose but may be derived fromfatty acids.Ans: E44. Which of the following statements about chylomicrons is FALSE?A. chylomicrons transport dietary lipids.B. chylomicrons are synthesized in the liver.C. chylomicron remnants are internalized by the liver.D. chylomicrons have a very high ratio of lipid to protein.E. Lipoprotein lipase catalyzes the hydrolysis of lipid from the chylomicrons.Ans: B45. In complete biosynthesis of sphingomyelin, all the following are required EXCEPTA. palmitoyl-CoA.B. L-serine.C. choline.D. CDP-diglyceride.E. NADPH.Ans: D

46. All of the following statements about chylomicron metabolism are true EXCEPTwhich one?A. chylomicrons donate apoprotein B to HDL.B. Another lipoprotein donates apoprotein C to chylomicrons.C. Lipoprotein lipase degrades chylomicron triglyceride.D. The end product of chylomicron metabolism in the circulation is called a remnantparticle.E. The liver removes the final component of chylomicron metabolism from thecirculation.Ans: A47. In the biosynthesis of cholesterol from Acetoacetyl CoA and Acetyl CoA, all of thefollowing metabolites are intermediates, EXCEPT:A. Dimethylallyl pyrophosphateB. Malonyl CoAC. Isopentenyl pyrophosphateD. MevalonateE. Farnesyl pyrophosphateAns: B

48. The acyl donor for cholesterol ester formation in blood isA. phosphatidylcholine.B. palmitoyl-CoA.C. triglycerides.D. acyl carrier protein.E. monoglycerides.Ans: A49. During cholesterol biosynthesis the production of HMG CoA involves acondensation reaction ofA.