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CARBOHYDRATE METABOLISM -- PRACTICE EXAM

RJ COHEN

1. All the following are termed common intermediates EXCEPT

a) pyruvate
b) glucose
c) acetyl CoA
d) citrate
e) oxaloacetate

2. Which is a TRUE statement?

a) anabolism and catabolism are balanced
b) anabolism is most active at low energy levels
c) the pathway for breaking down a complex macromolecule is generally not the reverse of the pathway for synthesizing it
d) anabolism is the breakdown of complex substances
e) the breakdown of proteins into amino acids yields energy in the form of ATP

3. Regulation of glycolysis is primarily through

a) phosphofructokinase
b) aldolase
c) pyruvate carboxylase
d) hexokinase
e) aconitase
O O

4. Product(s) of aldolase 1. CH-CHO(P)CH₂OH 2. HO-CH₂-C-CH₂O(P)

O O

3. CH-CHOH-CH₂O(P) 4. ^-O C-CHOH-CH₂O(P)

where (P) = phosphate in each case

a) 1 & 3
b) 2 only
c) 4 only
d) 2 &3
e) 3 & 4

5. The other reactant(s) when glyceraldehyde-3-phosphate is a substrate in one of the reactions in glycolysis:

a) phosphate and NAD⁺
b) ATP and NAD⁺
c) ATP
d) ADP
e) NADH

6. A difference between hexokinase and glucokinase:

a) one is exergonic, the other is not
b) one uses ATP as substrate, the other does not
c) glucokinase is not inhibited by glucose -6-phosphate while hexokinase is
d) hexokinase is not inhibited by glucose-6- phosphate while glucokinase is
e) hexokinase is found only in the liver while glucokinase is found in nearly every cell

7. Lactate fermentation and alcohol fermentation have in common

a) requirement for pyruvate decarboxylation
b) produce acetaldehyde as an intermediate
c) occur mostly in muscle
d) occur in the presence of abundant O₂
e) use up the NADHs produced by glycolysis

8. The Cori cycle involves

a) anerobic glycolysis in muscle and aerobic glycolysis in liver
b) anerobic glycolysis in muscle and gluconeogenesis in liver
c) aerobic glycolysis in muscle and gluconeogenesis in liver
d) glycolysis in the liver and gluconeogenesis in muscle
e) aerobic lactate production and glucose synthesis

9. Phosphofructokinase

a) activator = ATP; inhibitor = citrate
b) activator = ADP; inhibitor = fructose-2,6- phosphate
c) activator = fructose-2,6-phosphate; inhibitor = ATP
d) activator = acetyl CoA; inhibitor = ADP
e) activator = ATP; inhibitor = fructose-2,6-phosphate

10. A product of aerobic glycolysis

a) citrate
b) ribulose
c) ethanol
d) lactate
e) acetyl CoA

11. The enzyme that converts 2-phosphoglycerate to a high energy compound

a) aldolase
b) pyruvate kinase
c) enolase
d) 2-phosphoglycerate dehydrogenase
e) phosphoglycerate kinase

12, Higher than normal levels of a certain type of lactate dehydrogenase in the circulatory system is characteristic of

a) muscle fatigue
b) myocardial infarction
c) stroke
d) lactate intolerance
e) oxygen deficiency in the brain

13. To produce a molecule of glucose from pyruvate requires

         a) four ATP equivalents and two NADHs
         b) six ATP equivalents and one NADH
         c) six ATP equivalents and two NADHs
         d) eight ATP equivalents and two NADHs
         e) eight ATP equivalents and three NADHs

14. The enzymes used by gluconeogenesis to bypass key points in glycolysis include all EXCEPT:

                a) pyruvate kinase
                b) pyruvate carboxylase
                c) phosphoenolpyruvate carboxykinase
                d) fructose-1,6-bisphosphatase
                e) glucose-6-phosphatase

15. The phosphorylation of phosphofructokinase-2/fructose bisphosphatase-2

   a) is caused indirectly by insulin and leads to the inactivation of phosphofructokinase-2 and activation of fructose bisphosphatase-2
   b) is caused indirectly by insulin and leads to the inactivation of fructose bisphosphatase-2 and the activation of phosphofructokinase-2
   c) is caused by a NADH./acetyl CoA activated kinase
   d) is caused indirectly by glucagon and leads to the inactivation of phosphofructokinase-2 and activation of fructose bisphosphatase-2
   e) is caused indirectly by glucagon and leads to the inactivation of fructose bisphosphatase-2 and the activation of phosphofructokinase-2

16. Requires acetyl CoA

a) pyruvate kinase
  b) pyruvate carboxylase
  c) glucose-6-phosphatase
  d) fructose bisphosphatase
  e) phosphofructokinase

17. Fructose-2,6-bisphosphate

                a) inhibits fructose- 1,6-bisphosphatase and activates phosphofructokinase
                b) inhibits pyruvate carboxylase
                c) activates fructose- 1,6 -bisphosphatase
                d) inhibits phosphofructokinase
                e) stimulates a protein kinase

18. Located in the mitochondria

                a) phosphoglycerate kinase
                b) enolase
                c) phosphoenolpyruvate carboxykinase
                d) glucose 6-phosphatase
                e) pyruvate carboxylase

19, In glycogenesis, the glucose is always attached to the glycogen chain

                a) at the nonreducing end to form a 1 to 4 linkage
                b) at the reducing end to form a 1 to 4 linkage
                c) at the nonreducing end to form a 1 to 6 linkage
                d) at the reducing end to form a 1 to 6 linkage
                e) at the reducing end to form a 4 to 6 linkage

20. The debranching enzyme

   a) transfers a chain of any length from one branch of glycogen to the end of another branch
   b) transfers a chain of three glucoses from one branch of glycogen to the end of another branch
   c) transfers a chain of three glucoses to position 6 of a glucose in another chain
   d) removes glucose one at a time from a branch of glycogen as glucose phosphate
   e) removes a chain of glucose from glycogen and cleaves the chain to free glucose

21. Glycogen synthase uses which metabolite to add to glycogen?

a) glucose
b) glucose-1-phosphate
c) glucose-6-phosphate
d) UDP-glucose
e) GDP-glucose

22. Which would you expect NOT to stimulate glycogen phosphorylase activity (directly or indirectly)?

a) phosphorylation
b) cAMP
c) strenuous exercise
d) insulin
e) formation of the phosphorylase tetramer.

23. Protein kinase A

a) directly phosphorylates phosphorylase
b) directly phosphorylates phosphorylase kinase
c) phosphorylates G-protein
d) stimulates production of cAMP by adenylate cyclase
e) phosphorylates protein phosphatase

24. Muscle glycogen synthase

a) activated by phosphorylation and high levels of glucose-6-phosphate
b) activated by dephosphorylation and high levels of glucose-6- phosphate
c) inactivated by dephosphorylation
d) inactivated by high levels of glucose-6-phosphate
e) activated by acetyl CoA

25. Branch formation in glycogenesis

a) by growth from an existing chain
b) by the transfer of an entire branch
c) by the transfer of part of a branch to another branch
d) by the addition of an oligosaccharide ( a chain of glucoses)
e) by branched growth

26. Which of the following cofactors is NOT involved in the formation of acetyl CoA from pyruvate by pyruvate dehydrogenase complex?

                    a) biotin
                    b) FAD/FADH₂
                    c) lipoamide
                    d) NAD⁺/NADH
                    e) thiamine pyrophosphate

27. Succinate to fumarate to malate

                a) oxidative decarboxylation followed by a dehydration
                b) oxidative decarboxylation followed by a hydration
                c) dehydrogenation followed by a hydration
                d) dehydrogenation followed by a dehydration
                e) hydration followed by a dehydrogenation

28. Starting with acetyl CoA entering the TCA cycle and going through the cycle once, the maximum total number of ATP equivalents from acetyl CoA metabolism is:

a) 2 b) 10 c) 11 d) 12 e) 13

29. The structure of isocitrate:

a) CH₂-COO^- b) CH₂-COO^-    c) CH₂-COO^-    d) CH₂-COO^-      e) O=C-COO^-
   HC-COO^-         C-COO^-       HOC-COO^-            C=O                         CH₂
HOC-COO^-HC-COO^-HC-COO^-      HOC-COO^-                 HC-COO^-
      H                    H                        H                       H                               H

30. An enzyme that catalyzes a substrate level phosphorylation in the TCA cycle:

a) citrate synthase
b) isocitrate dehydrogenase
c) ketoglutarate dehydrogenase
d) succinyl CoA synthetase
e) succinate dehydrogenase

31. The carboxylation of pyruvate to form oxaloacetate is an example of what type of reaction?

a) amphibolic b) anaphylactic c) hydrolytic d) anaplerotic e) depletionary

32. The conversion rate of pyruvate to CO₂ and H₂O is decreased:

                a) in the presence of high ADP/ATP ratio
                b) in the presence of high NADH/NAD⁺ ratio
                c) allosterically by low succinyl CoA concentrations
                d) both b) and c)
                e) both a) and c)

33. Two important functions of the pentose phosphate shunt.

                a) producing ATP and pentose phosphates
                b) producing NADPH and removing pentose phosphates
                c) producing pentose phosphates and triose phosphates
                d) producing NADH and pentose phosphates
                e) producing NADPH and pentose phosphates

34. An enzyme that produces a lactone.

a) lactone synthase b) ribose epimerase c) lactonase d) glucose-6-phosphate dehydrogenase
e) 6- phosphogluconate dehydrogenase

35. Which of the following is a flavoprotein?

            a) NADH dehydrogenase
            b) ubiquinone
            c) cytochrome oxidase = cytochrome aa₃
            d) succinate dehydrogenase
            e) both a) and d)

36. Contains heme or a modified hem

a) NADH dehydrogenase b) iron sulfur center c) ubiquinone d) cytochromes e) complex I

37. Hydride transfer

a) FAD b) ubiquinone c) NAD d) iron sulfur center e) heme

38. Which entity receives electrons directly from a mobile carrier?

a) cytochrome a₃b) CoQ c) cytochrome b d) cytochrome c e) complex V

39. Which is the correct order for the transport of electrons?

            a) CoQ to cyt a to cyt a₃ to cyt b to cyt c to cyt c₁
            b) CoQ to cyt c to cyt c₁ to cyt b to cyt a to cyt a₃
            c) cyt b to CoQ to cyt c₁ to cyt c to cyt a to cyt a₃
            d) CoQ to cyt b to cyt c₁ to cyt c to cyt a to cyt a₃
            e) CoQ to cyt b to cyt c₁ to cyt c to cyt a₃ to cyt a

40. Which entity reacts directly with oxygen in electron transport?

a) cytochrome aa₃b) cytochrome b c) NADH d) cytochrome c e) ubiquinone

41. The number of potential ATPs that can be produced

            a) two per NADH; three per FADH₂
            b) three per NADH; two per FADH₂
            c) two per NADH; two per FADH₂
            d) one per NADH; two per FADH₂
            e) two per NADH; one per FADH₂

42. Respiratory control refers to:

            a) the dependence of oxygen utilization on the presence of ATP
            b) the dependence of phosphorylation of ADP on the presence of uncouplers
            c) the dissociation of oxygen utilization from ATP formation
            d) the dissociation of oxygen utilization from electron flow
            e) the requirement of ADP and phosphate for oxygen utilization

43. All of the following are requirements for the chemiosmotic mechanism of oxidative phosphorylation EXCEPT:

            a) an intact, proton impermeable inner mitochondrial membrane
            b) an ATP synthase complex, driven by a proton gradient
            c) mechanisms to pump protons into the mitochondrial matrix
            d) mechanisms to couple electron transport to proton pumping
            e) all of the above are required

44. The Pasteur effect

a) glucose consumption decreases, lactate production decreases, oxygen comsumption increases
b) glucose consumption increases, lactate production increases, oxygen consumption decreases
c) glucose consumption decreases, lactate production decreases, oxygen consumption decreases
d) glucose consumption increases, lactate production increases, oxygen consumption increases
e) glucose consumption increases, lactate production decreases, oxygen comsumption increases

45. A mechanism for transferring electron pair equivalents into the mitochondria

            a) adenine nucleotide translocase
            b) dihydroxyacetone phosphate shuttle
            c) malate/succinate shuttle
            d) malate/oxaloacetate shuttle
            e) b) and d)

46. Addition of the uncoupler, 2,4 dinitrophenol, to a tightly coupled mitochondrion undergoing oxidative phosphorylation:

            a) decreases the rate of ADP phosphorylation
            b) decreases the rate of electron transport
            c) decreases the utilization of oxygen
            d) increases the rate of electron transport
            e) increases the rate of ADP phosphorylation

47. Which of the following indirectly generates an ATP?

                a) transfer of electrons from CoQ to a cytochrome
                b) transfer of electrons from succinate dehydrogenase to an acceptor
                c) oxidation of cytochrome aa₃
                d) transfer of electrons from cytochrome c to cytochrome a
                e) transfer of electrons from cytochrome c to cytochrome c₁

48. The ATP synthase

a) allows protons to flow into the matrix and thereby generates three ATPs per one rotation
b) allows protons to flow out of the matrix and thereby rotates three times to make one ATP
c) allows electrons to pass through to generate ATP
d) allows protons to flow out of the matrix and thereby generates three ATPs per one rotation
e) allows protons to flow into the matrix and thereby rotates three times to make one ATP

49. Microsomal P450 is an example of a(n)

a) dismutase b) oxidase c) hydroxylase d) oxygenase e) detoxicase

50. Peroxide

  a) is destroyed by catalase because it is toxic
  b) is destroyed by a dismutase because it is toxic
  c) is make by an oxygenase because it is required for metabolites requiring peroxide
  d) is made by catalase
  e) is used by phenylalanine monooxygenase

ANSWERS: 1. b 2. c 3. a. 4. d 5. a 6. c 7. e 8. b 9. c 10. e 11. c 12. b 13. c 14. a 15. d 16. b 17. a 18. e 19. a 20. b 21. d 22. d 23. b 24. b 25. c 26. a 27. c 28. d 29. a 30. d 31.d 32. b 33. e 34. d 35. e 36. d 37. c 38. c 39. d 40. a 41. b 42. e 43. c 44. a 45. e 46. a 47. c 48. a 49. d 50. a