CHE242 Basic Biochemistry: Exam 4 practice questions.

Multiple choice. For each choose the one best answer.

1. Which of the following molecules is most likely produced by cellular catabolism?

A. Proteins

B. Lipids

C. Carbon dioxide (CO2)

D. Oxidized form of nicotinamide adenine dinucleotide (NAD+)

2. What class of enzymes uses nicotinamide adenine dinucleotide in oxidation-reduction reactions?

A. Dehydrogenases

B. Isomerases

C. Transaminases

D. Kinases

3. Biological oxidation-reduction reactions always involve:

A. direct participation of oxygen.

B. formation of water.

C. transfer of hydrogens.

D. transfer of electron(s).

4. Which of the following reactions of glycolysis is irreversible?

A. glucose 6-phosphate fructose 6-phosphate.

B. fructose 1,6-bisphosphate dihydroxyacetone phosphate + glyceraldehyde 3-phosphate.

C. fructose 6-phosphate fructose 1,6-bisphosphate.

D. dihydroxyacetone phosphate glyceraldehyde 3-phosphate.

5. The effect of fructose 1,6-bisphosphate on pyruvate kinase is an example of

A. feedback inhibition.

B. feed-forward activation.

C. activation by phosphorylation.

D. activation by dephosphorylation.

6. Complete the following sentence by filling in the blanks. In the triose phase of glycolysis, the conversion of

glyceraldehyde 3-phosphate to pyruvate, ___ molecules of ATP and ____ molecules of NADH are produced per

molecule of glucose.

A. 2, 2

B. 2, 1

C. 4, 2

D. 32, 10

7. Which of the following molecules, in high concentration, activates the glycolytic enzyme phosphofructokinase-1?

A. citrate

B. ATP

C. AMP

D. 2,3-bisphosphoglycerate

8. The enzyme Phosphofructokinase (PFK-1) is allosterically regulated. Which is not a regulatory effect?

A. AMP activates PFK-1.

B. Protons activate PFK-1.

C. Fructose 2,6-bisphosphate activates PFK-1.

D. ATP inhibits PFK-1.

9. If glycolysis converts glucose to pyruvate and then pyruvate to lactic acid this is an example of:

A. anaerobic metabolism.

B. anabolic metabolism.

C. a net reductive process.

D. oxidative phosphorylation

10. During strenuous exercise, NADH formed by glycolysis in skeletal muscle must be reoxidized to NAD+ if glycolysis is to

continue. The most important reaction involved in the reoxidation of NADH is:

A. dihydroxyacetone phosphate glycerol 3-phosphate

B. glucose 6-phosphate fructose 6-phosphate

C. pyruvate lactate

D. oxaloacetate malate

11. Conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate results in a net formation of:

A. 1 mol of NAD+ and 2 mol of ATP.

B. 1 mol of NADH and 1 mol of ATP.

C. 2 mol of NAD+ and 4 mol of ATP.

D. 2 mol of NADH and 4 mol of ATP.

12. When a muscle contracts aerobically, less lactic acid is formed than when it contracts anaerobically because:

A. glycolysis does not occur to significant extent under aerobic conditions.

B. muscle is metabolically less active under aerobic than anaerobic conditions.

C. under aerobic conditions most pyruvate is oxidized by the citric acid cycle rather than reduced to lactate.

D. the major energy-yielding pathway in muscle is the pentose phosphate pathway, which does not produce lactate.

13. The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except:

A. ATP synthesis.

B. catalysis by phosphoglycerate kinase.

C. oxidation of NADH to NAD+.

D. utilization of pyrophosphate (Pi).

14. Which of the following is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

A. ATP

B. Cu2+

C. heme

D. NAD+

15. Pyruvate kinase is allosterically inhibited by:

A. high concentrations of AMP.

B. high concentrations of ATP.

C. high concentrations of citrate.

D. low concentrations of acetyl-CoA.

16. Which is TRUE about the molecule fructose 2,6-bisphosphate?

A. It is produced from fructose 1,6-bisphosphate.

B. It is an activator of phosphofructokinase-1.

C. It serves as a regulator of oxygen binding by hemoglobin.

D. It is an intermediate in glycolysis that is converted to glyceraldehyde 3-phosphate and dihydroxyacetone phosphate.

17. Which cellular situation would result in activation of the pyruvate dehydrogenase complex?

A. high concentration of ATP

B. high concentration of NAD+

C. high concentration of acetyl-CoA

D. high concentration of NADH

18. Which of the following is TRUE of the citric acid cycle?

A. Enzymes of the cycle are cytoplasmic, except succinate dehydrogenase, which is bound to the mitochondrial membrane.

B. If NADH is present in high concentrations, one would expect the citric acid cycle to be inhibited.

C. Intermediates of the cycle contain either one or two phosphates.

D. Isocitrate dehydrogenase channels electrons directly into the electron transfer chain.

19. In eukaryotes the enzymes of the citric acid cycle are found in the

A. Cytosol

B. Mitochondria

C. Endoplasmic reticulum

D. Nucleus

20. The only reaction in the citric-acid cycle in which a carbon-carbon bond is formed is catalyzed by

A. citrate synthase

B. isocitrate dehydrogenase

C. succinyl-CoA synthetase

D. fumarase

21. Which enzyme does not catalyze a reaction that releases carbon dioxide (CO2)?

A. -ketoglutarate dehydrogenase complex

B. pyruvate dehydrogenase

C. malate dehydrogenase

D. isocitrate dehydrogenase

22. An increase in the concentration of which of the following molecules in a cell would result in an increase in the rate of

the citric acid cycle?

A. Adenosine triphosphate (ATP).

B. NADH.

C. Coenzyme A.

D. Adenosine diphosphate (ADP).

23. Which molecule is a crucial intermediate at the branch point of the glyoxylate and citric acid cycles?

A. citrate

B. isocitrate.

C. oxaloacetate.

D. -ketoglutarate.

24. What process allows certain organisms to synthesize carbohydrate from acetyl-CoA?

A. pentose-phosphate pathway.

B. citric acid cycle.

C. glycolysis.

D. glyoxylate cycle.

25. How many ATP molecules result from the complete oxidation of one molecule of acetyl-CoA to CO2 and H2O? This

includes ATP molecules directly synthesized in the citric acid cycle as well as those that result from the transfer of

electrons to molecular oxygen.

A. 10

B. 9

C. 8.5

D. 11

26. The pentose phosphate pathway produces what energy-rich molecule? A. NADPH

B. NAD+

C. FAD

D. ATP

27. Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex?

A. Biotin participates in the decarboxylation.

B. Both NAD+ and a flavin nucleotide act as electron carriers.

C. The reaction occurs in the mitochondrial matrix.

D. The substrate is held by the lipoyl-lysine “swinging arm.”

28. Which of the below is not required for the oxidative decarboxylation of pyruvate to form acetyl-CoA?

A. ATP

B. Coenzyme A

C. FAD

D. Lipoic acid

29. Which of the following is not an intermediate of the citric acid cycle?

A. Glyoxylate

B. Citrate

C. Oxaloacetate

D. Succinyl-CoA

30. In mammals, each of the following occurs during the citric acid cycle except:

A. formation of -ketoglutarate.

B. generation of NADH and FADH2.

C. reduction of acetyl-CoA.

D. dehydrogenation of malate

31. Conversion of 1 mol of acetyl-CoA to 2 moles of CO2 via the citric acid cycle results in the net production of:

A. 7 moles of ATP.

B. 1 mole of FADH2.

C. 1 mole of NADH.

D. 1 mole of oxaloacetate.

32. The oxidative decarboxylation of -ketoglutarate proceeds by means of multistep reactions in which all but one of the

following cofactors are required. Which one is not required?

A. ATP

B. Coenzyme A

C. Thiamine pyrophosphate

D. NAD+

33. Which one of the following enzymatic activities would be decreased by thiamine deficiency?

A. Fumarase

B. Isocitrate dehydrogenase

C. -Ketoglutarate dehydrogenase complex

D. Succinate dehydrogenase

34. The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) is the conversion of

A. citrate to isocitrate.

B. succinyl-CoA to succinate

C. malate to oxaloacetate.

D. succinate to fumarate.

35. All of the oxidative steps of the citric acid cycle are linked to the reduction of NAD+ except the reaction catalyzed by:

A. isocitrate dehydrogenase.

B. malate dehydrogenase.

C. pyruvate dehydrogenase

D. succinate dehydrogenase.

36. The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields

_____ mol of NADH, _____ mol of FADH2, and _____ mol of ATP (or GTP).

A. 2; 2; 2

B. 3; 1; 1

C. 4; 2; 1

D. 4; 1; 1

37. Entry of acetyl-CoA into the citric acid cycle is decreased when:

A. [AMP] is high.

B. NADH is rapidly oxidized through the respiratory chain.

C. the ratio of [NAD+]/[NADH] is high.

D. the ratio of [ATP]/[ADP] is high.

38. Isocitrate dehydrogenase is inhibited by high concentrations of

A. acetyl-CoA and fructose 6-phosphate.

B. ATP and/or NADH.

C. AMP and/or NADH.

D. ATP and/or NAD+.

39. During seed germination, the glyoxylate pathway is important to plants because it enables them to:

A. carry out the net synthesis of glucose from acetyl-CoA.

B. form acetyl-CoA from malate.

C. get rid of isocitrate formed from the aconitase reaction.

D. obtain glyoxylate for cholesterol biosynthesis.

40. A function of the glyoxylate cycle, in conjunction with the citric acid cycle, is to accomplish the:

A. complete oxidation of acetyl-CoA to CO2 plus reduced coenzymes.

B. net conversion of lipid to carbohydrate.

C. formation of glucose from sunlight.

D. net synthesis of long-chain fatty acids from citric acid cycle intermediates.

41. Vitamin deficiencies can have a profound effect on metabolism. Which enzyme would be affected by a deficiency of

niacin?

a. Hexokinase

b. Glyceraldehyde 3-phosphate dehydrogenase

c. citrate synthase

d. succinate dehydrogenase

42. What is the only enzyme of the citric acid cycle that is membrane-bound?

a. Hexokinase

b. Glyceraldehyde 3-phosphate dehydrogenase

c. citrate synthase

d. succinate dehydrogenase

43. When glucose is needed by the body during periods of starvation, what organ or tissue supplies it?

a. adipose tissue

b. liver

c. brain

d. intestine

44. Which of the following pathways in the liver are stimulated by glucagon?

a. gluconeogenesis

b. glycogen synthesis

c. glycolysis

d. all of the above

45. What are the enzymes of gluconeogenesis that bypass irreversible steps of glycolysis?

A. hexokinase, phosphofructokinase, phosphoglycerate kinase

B. phosphofructokinase, pyruvate phosphatase, glucose decarboxylase

C. pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-bisphosphatase, glucose 6-phosphatase

D. pyruvate kinase, phosphoenolpyruvate dehydrogenase, fructose 6-phosphatase, glucose 6-kinase

46. Which of the following pathways in the liver are stimulated by insulin?

A. gluconeogenesis

B. glycogen synthesis

C. beta oxidation of fatty acids

D. all of the above

47. An increase in the concentration of which of the following molecules would increase the rate of gluconeogenesis?

A. glucose

B. fructose 2,6-bisphosphate

C. acetyl-CoA

D. adenosine diphosphate (ADP)

48. Which molecule is a substrate for glycogen synthesis?

A. glucose-6-phosphate

B. ADP-glucose

C. UDP-glucose

D. glucose 1,6-bisphosphate

49. Glycogen is converted to monosaccharide units by:

A. glucokinase.

B. glucose-6-phosphatase

C. glycogen phosphorylase.

D. glycogen synthase.

50. Which compound cannot serve as the starting material for the synthesis of glucose via gluconeogenesis?

A. acetate

B. glycerol

C. lactate

D. oxaloacetate

51. An enzyme used in both glycolysis and gluconeogenesis is:

A. glyceraldehyde 3-phosphate dehydrogenase

B. glucose 6-phosphatase.

C. hexokinase.

D. phosphofructokinase-1.

52. Which one of the following statements about gluconeogenesis is false?

A. For starting materials, it can use carbon skeletons derived from certain amino acids.

B. It consists entirely of the reactions of glycolysis, operating in the reverse direction.

C. It employs the enzyme glucose 6-phosphatase.

D. It requires metabolic energy (ATP or GTP).

53. In humans, gluconeogenesis:

A. can result in the conversion of protein into blood glucose.

B. helps to reduce blood glucose after a carbohydrate-rich meal.

C. is activated by the hormone insulin

D. is essential in the conversion of fatty acids to glucose.

54. The metabolic function of the pentose phosphate pathway is:

A. act as a source of ADP biosynthesis.

B. generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.

C. participate in oxidation-reduction reactions during the formation of H2O.

D. provide intermediates for the citric acid cycle.

55. The glycogen debranching enzyme catalyzes:

A. degradation of ( 1 6) linkages in glucose

B. formation of ( 1 4) linkages in glucose.

C. formation of ( 1 6) linkages during glycogen synthesis.

D. formation of fructose 6-phosphate

56. Which of the following statements about gluconeogenesis in animal cells is true?

A. A rise in the cellular level of fructose-2,6-bisphosphate stimulates the rate of gluconeogenesis.

B. The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is catalyzed by phosphofructokinase-1.

C. The conversion of glucose 6-phosphate to glucose is catalyzed by hexokinase.

D. The conversion of pyruvate to phosphoenolpyruvate occurs in two steps, including a carboxylation.

57. There is reciprocal regulation of glycolytic and gluconeogenic reactions interconverting fructose-6-phosphate and

fructose-1,6-bisphosphate. Which one of the following statements about this regulation is not correct?

A. Fructose-2,6-bisphosphate activates phosphofructokinase-1.

B. Fructose-2,6-bisphosphate inhibits fructose-1,6-bisphosphatase.

C. The fructose-1,6-bisphosphatase reaction is exergonic.

D. The phosphofructokinase-1 reaction is endergonic.

58. Which of the following is true of glycogen synthesis and breakdown?

A. Phosphorylation activates the breakdown enzyme and inactivates the synthetic enzyme.

B. Synthesis is catalyzed by the same enzyme that catalyzes breakdown.

C. The glycogen molecule “grows” at its reducing end.

D. The immediate product of glycogen breakdown is free glucose.

59. Glycogen phosphorylase a can be inhibited by high concentrations of

A. AMP.

B. calcium.

C. GDP.

D. glucagon.

60. Which one of the following directly results in the activation of glycogen synthase?

A. Binding of glucose-6-phosphate

B. Insulin

C. Glycosylation of glycogen synthase

D. Epinephrine

61. Which of the following best describes the Cori cycle?

a. Glycolysis in the liver is coordinated with gluconeogenesis in the muscle.

b. It involves anaerobic catabolism in the liver.

c. The liver synthesizes glucose from lactate produced in the muscle

d. Alanine is used to carry amino groups to the liver.

62. Which statement is TRUE regarding reciprocal regulation of glycogen synthesis and degradation?

a. Glycogen synthase and glycogen phosphorylase need to be phosphorylated to be maximally active.

b. Glycogen phosphorylase is inhibited by glucose 6-phosphate while glycogen synthase is activated by glucose 6-phosphate.

c. Glycogen is synthesized from glucose but is broken down to yield ribose.

d. Glycogen synthesis occurs in the cytosol while glycogen breakdown occurs in the nucleus.

63. With respect to the -oxidation of stearate which is true?

A. -oxidation results in production of 8 acetyl-CoA, 7 NADH and 7 FADH2.

B. -oxidation results in production of 9 acetyl-CoA, 9 NADH and 9 FADH2.

C. -oxidation results in production of 8 acetyl-CoA, 8 NADH and 8 FADH2.

D. -oxidation results in production of 9 acetyl-CoA, 8 NADH and 8 FADH2.

64. Fill in the blank in the following senetence. In the catabolism of isoleucine the carbon skeleton enters the citric acid

cycle as acetyl-CoA. Isoleucine is therefore called a ____________________ amino acid.

A. aminogenic

B. diabetic

C. ketogenic

D. glucogenic

65. An increase in the concentration of which of the following molecules in a cell would most likely result in an increased

production of the waste molecule urea?

A. palmitic acid

B. pyruvate

C. glutamate

D. Adenosine diphosphate (ADP).

66. Lipoprotein lipase acts in:

A. hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues.

B. intestinal uptake of dietary fat.

C. intracellular lipid breakdown of lipoproteins.

D. lipoprotein breakdown to supply needed amino acids.

67. The role of hormone-sensitive triacylglycerol lipase is to:

A. hydrolyze lipids stored in the liver.

B. hydrolyze membrane phospholipids in hormone-producing cells.

C. hydrolyze triacylglycerols stored in adipose tissue.

D. synthesize lipids in adipose tissue.

68. Saturated fatty acids are degraded by the stepwise reactions of oxidation, producing acetyl-CoA. Under aerobic

conditions, how many ATP molecules would be produced as a consequence of removal of each acetyl-CoA?

A. 2

B. 3

C. 4

D. 5

69. In amino acid catabolism, the first reaction for many amino acids is a(n):

A. decarboxylation requiring thiamine pyrophosphate (TPP).

B. hydroxylation requiring NADPH and O2.

C. oxidative deamination requiring NAD+.

D. transamination requiring pyridoxal phosphate (PLP).

70. If a person's urine contains unusually high concentrations of urea, which one of the following diets has he or she

probably been eating recently?

A. High carbohydrate, very low protein

B. Very high carbohydrate, no protein, no fat

C. Very low carbohydrate, very high protein

D. Very high fat, very low protein

71. In the electron transport chain the overall flow of electrons is from

A. NADH and QH2 to O2

B. O2 to NAD+ and Q

C. O2 to NADH

D. ATP to O2

72. In the reoxidation of reduced coenzyme Q (QH2) by purified Complex III from heart muscle, the overall stoichiometry

of the reaction requires two mol of cytochrome c per mole of QH2 because:

A. cytochrome c is a two electron acceptor, whereas QH2 is a one electron donor

B. cytochrome c is a one electron acceptor, whereas QH2 is a two electron donor

C. two molecules of cytochrome c must first physically combine before they are catalytically active

D. heart muscle has a high rate of oxidative metabolism, and therefore requires twice as much cytochrome c as QH2 for

electron transfer to proceed normally.

73. How many protons must flow through the Fo subunit of ATP synthase for the F1 subunit of ATP synthase to synthesize

one molecule of ATP?

A. 3

B. 4

C. 6

D. 10

74. With respect to the -oxidation of myristate which is true?

A. -oxidation results in production of 8 acetyl-CoA, 7 NADH and 7 FADH2.

B. -oxidation results in production of 8 acetyl-CoA, 7 NADH and 7 FADH2.

C. -oxidation results in production of 7 acetyl-CoA, 7 NADH and 7 FADH2.

D. -oxidation results in production of 7 acetyl-CoA, 6 NADH and 6 FADH2.

75. Oxidation of one glucose molecule by glycolysis results in two molecules of pyruvate, which are converted to two

molecules of acetyl-CoA. How many ATP (or GTP) molecules result from the complete oxidation of these two

molecules of acetyl-CoA to CO2 and H2O? This includes ATP (or GTP) molecules directly synthesized in the citric

acid cycle as well as those that result from the transfer of electrons to molecular oxygen. A. 20

B. 18

C. 10

D. 12

76 Where in a eukaryotic cell are the proteins of oxidative phosphorylation located?

A. Inner mitochondrial membrane

B. Plasma membrane

C. Cytoplasm

D. Nucleus

77. How many molecules of ATP are synthesized as a result of the transfer of electrons from NADH to oxygen through the

electron transfer chain?

A. 1.5

B. 2

C. 2.5

D. 4

78. Which of the following statements about oxidative phosphorylation is FALSE?

A. The proteins that make up the electron transport chain are associated with the inner mitochondrial membrane

B. The electron transport chain pumps protons from the mitochondrial matrix to the intermembrane space.

C. Malate dehydrogenase, a citric acid cycle enzyme, transfers electrons from FADH2 to the electron transport chain.

D. The electron transport chain accepts electrons from NADH and FADH2.

79. What citric acid cycle enzyme is also a component of the electron transport chain in oxidative phosphorylation?

A. Succinate dehydrogenase

B. Fumarate dehydrogenase

C. Malate dehydrogenase

D. -ketoglutarate dehydrogenase

80. The energy of electron transfer from NADH and FADH2 is efficiently conserved in what form?

A. triacylglycerols

B. glycogen

C. carbon dioxide (CO2)

D. a proton gradient

81. How many protons are pumped out of the mitochondrial matrix for every NADH molecule oxidized to NAD+?

A. 2

B. 4

C. 6

D. 10

82. How many protons are pumped out of the mitochondrial matrix for every FADH2 molecule oxidized to FAD?

A. 2

B. 4

C. 6

D. 10

83. Mitochondrial F1 subunit of ATP synthase has nine subunits of five different types ( 3 3 ). How many catalytic sites

for ATP synthesis are present in the F1 subunit of ATP synthase?

A. 1

B. 2

C. 3

D. 4

84. Which component of the electron transport chain is a lipid soluble molecule with an isoprenoid chain?

A. cytochrome c

B. NADH:ubiquinone oxidoreductase (Complex I)

C. ubiqinone (Coenzyme Q)

D. malate dehydrogenase

85. The cytochromes are proteins involved in electron transport. What prosthetic group do cytochromes contain?

A. thiamine pyrophosphate (TPP)

B. Ubiquinone (Coenzyme Q)

C. a heme containing an iron

D. Coenzyme A

86. Which of the following is correct concerning the mitochondrial ATP synthase?

A. It can synthesize ATP after it is extracted from broken mitochondria.

B. It catalyzes the formation of ATP

C. It consists of F0 and F1 subunits, which are transmembrane (integral) polypeptides.

D. It is actually an ATPase and only catalyzes the hydrolysis of ATP.

87. During oxidative phosphorylation, the proton gradient that is generated by electron transport is used to:

A. reduce O2 to H2O.

B. generate the substrates (ADP and Pi) for the ATP synthase.

C. induce a conformational change in the ATP synthase.

D. oxidize NADH to NAD+.

88. Energy of electron transfer from NADH and FADH2 to O2 is conserved in the form of

a. glycogen

b. amino acids

c. a proton gradient

d. carbon dioxide (CO2)

89. How many protons are pumped out of the mitochondrial matrix when the electrons from one molecule of FADH2 are

transferred to oxygen?

a. 4

b. 6

c. 8

d. 10

90. What is the function of the isoprenoid chain portion of coenzyme Q (ubiquinone)?

a. It undergoes reversible oxidation and reduction.

b. It is critical for the transfer of electrons.

c. It is important for making coenzyme Q soluble in the lipid bilayer.

d. It pumps protons across the inner mitochondrial membrane.

Glucose metabolism.

1. Below is depicted glucose catabolism. Indicate on the pathways the following: A) which reaction(s) of glycolysis are

irreversible B) where energy rich molecules are produced, such as NADH, FADH2 and ATP or GTP C) Where carbon

molecules are released as waste D) two examples of inhibition by high concentrations of a metabolite E) two examples

of activation by high concentrations of a metabolite.

Glucose

Glucose 6-phosphate

Fructose 6-phosphate

Fructose 1,6-bisphosphate

Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate

1,3-bisphosphoglycerate

3-phosphoglycerate

2-phosphoglycerate

phosphoenolpyruvate

pyruvate

Acetyl-CoA

oxaloacetate citrate

isocitrate

-ketoglutarate

Succinyl-CoA succinate

fumarate

malate

Part IX. Oxidative phosphorylation.

1. The goal of glucose oxidation is to produce adenosine triphosphate (ATP) for the synthesis of biomolecules in the cell.

Explain how the electrons extracted from glucose are used to synthesize ATP. Make sure to include in your discussion

necessary enzymatic cofactors, location of processes in a mammalian cell, proteins and enzymes used in the process, the

energy source for the process, and the ultimate fate of the electrons and newly synthesized ATP.