3.3 Enzymes and Energy
29. Enzymes which remove hydrogen atoms from their substrates are referred to as A. dehydrogenases. B. hydrolases. C. catalases. D. peroxidases.
A
73. The greatest increase in entropy occurs A. when starch is degraded to glucose. B. when amylase produces maltose. C. when glucose is converted to galactose. D. when ATP is synthesized.
A
94. During reduction, a molecule or atom A. gains protons or gains electrons. B. loses protons or gains electrons. C. gains protons or loses electrons. D. loses protons or loses electrons.
A
32. Hydrolysis reactions are catalyzed by A. dehydrogenases. B. hydrolases. C. isomerases. D. synthases.
B
30. The breakdown of hydrogen peroxide is catalyzed by A. aldolase. B. amylase. C. catalase. D. kinase.
C
31. Addition of phosphate groups to a particular molecule is catalyzed by A. transaminases. B. phosphatases. C. isomerases. D. kinases.
D
33. Dehydration synthesis reactions are catalyzed by A. dehydrogenases. B. hydrolases. C. isomerases. D. synthases.
D
34. Pancreatic amylase catalyzes the breakdown of oligosaccarides to disaccharides with the addition of water. What classification of enzymes would amylase be in? A. dehydrogenase B. isomerase C. synthase D. hydrolase
D
41. The enzyme with the lowest pH optimum is A. acid phosphatase. B. lipase. C. monoamine oxidase. D. pepsin.
D
45. Which of the following is NOT true about enzymes? A. As the temperature increases from 25C to 37C enzyme activity decreases. B. Very few enzymes require cofactors. C. Most enzymes are not sensitive to changes in pH. D. All are not true.
D
1. Most enzymes are lipids.
FALSE
25. Isomers are different forms of an enzyme.
FALSE
26. Isoenzymes bind different substrates and catalyze different chemical reactions.
FALSE
27. Abnormally high concentration of the BB form of creatine phosphokinase is associated with a myocardial infarction.
FALSE
49. At saturation, enzyme activity is maximal.
TRUE
9. The vitalist concept was defeated because of fermentation experiments involving A. yeast. B. bacteria. C. amoebae. D. paramecia.
a
15. The model that explains how an enzyme and substrate fit together is the A. enzyme-substrate model. B. lock-and-key model. C. conformational model. D. None apply.
b
7. Enzymes ______________ the rate of a specific chemical reaction. A. decrease B. increase C. have no effect on
b
8. The rate at which a chemical reaction can be increased is by either ______________ the temperature or ______________ the activation energy. A. increasing, increasing B. increasing, decreasing C. decreasing, decreasing D. decreasing, increasing
b
12. Biological catalysts A. decrease reaction rates. B. alter a reaction product. C. remain unchanged at the end of the reaction. D. All apply.
c
16. The model that describes how an enzyme can adjust its shape to fit the shape of the substrate is the A. lock-and-key model. B. enzyme-substrate model. C. induced-fit model. D. conformational model.
c
19. When an enzyme catalyzes a chemical reaction A. the enzyme binds to the substrate's active site. B. the enzyme's active site binds the product. C. amino acids in the substrate allow for interaction with the product. D. amino acids in the enzyme's active site interact with substrate molecules.
d
21. Elevated plasma amylase could indicate A. osteitis deformans. B. a myocardial infarct. C. obstructive jaundice. D. a perforated peptic ulcer.
d
35. Which of the following does NOT affect the activity of an enzyme? A. the organ the enzyme is in B. concentration of enzyme and substrate molecules C. concentration of cofactors and coenzymes D. pH and temperature
A
40. The phosphatase found in bone would have a pH optimum that is ______________ than the pH optimum of the phosphatase found in the prostate gland. A. higher B. lower C. the same as
A
57. ______________ occurs when the product of a metabolic pathway binds to an enzyme and decreases enzymatic activity. A. Allosteric inhibition B. End-product therapy C. Second messaging D. Coupling
A
58. A defect in the enzyme which converts phenylalanine into tyrosine is characteristic of the disease A. phenylketonuria. B. albinism. C. lactose intolerance. D. maple-syrup disease.
A
61. Decreased phenylalanine metabolism causes A. albinism. B. hypercholeteremia. C. lactose intolerance. D. Tay-Sachs disease.
A
67. Energy transformations result in a(n) ______________ in entropy. A. increase B. decrease C. no change
A
68. Cellular respiration results in a(n) ______________ in entropy as glucose is broken down to form carbon dioxide. A. increase B. decrease C. no change
A
71. Energy can change forms, but cannot be created or destroyed is a statement of the A. first law of thermodynamics. B. second law of thermodynamics. C. law of mass action. D. third law of thermodynamics.
A
91. Oxidized nicotinamide adenine dinucleotide (NAD) has ______________ two hydrogens. A. lost B. gained C. shared
A
98. FAD and NAD are coenzymes that act as _______ in biochemical reactions. A. hydrogen carriers B. oxygen carriers C. energy carriers D. vitamin carriers
A
42. In an enzymatic reaction, when temperature is increased past the point of "optimal temperature," the enzyme starts to A. increase its catalytic activity. B. reduce its catalytic activity. C. increase its allosteric properties. D. increase product formation.
B
46. Which of the following is NOT true of catalysts? A. They are unchanged by the reaction catalyzed. B. They allow endergonic reactions to become exergonic reactions. C. They increase the amount of energy released by a chemical reaction. D. They lower the activation energy of the reaction.
B
51. In the reaction (H2O + CO2 H2CO3), increasing the concentration of H2O would A. decrease the concentration of H2CO3. B. increase the concentration of H2CO3. C. increase the concentration of CO2. D. have no effect on either CO2 or H2CO3 concentrations.
B
59. A defect in the enzyme that catalyzes the formation of melanin from DOPA results in A. phenylketonuria. B. albinism. C. lactose intolerance. D. maple-syrup disease.
B
62. An inborn error in lipid metabolism may cause all of the following diseases EXCEPT A. Tay-Sachs disease. B. homocystinuria. C. hypercholesteremia. D. Gaucher's disease.
B
63. What technique has been affective in the treatment of inborn errors of metabolism such as SCID? A. allosteric inhibition B. gene therapy C. coenzyme activation D. None of the choices is correct.
B
70. Energy transformations increase the entropy of a system is a statement of the A. first law of thermodynamics. B. second law of thermodynamics. C. law of mass action. D. law of conservation of energy.
B
75. Free energy is ______________ when exergonic reactions proceed. A. increased B. decreased C. unchanged
B
76. Endergonic reactions cause the amount of entropy in the products to be A. increased. B. decreased. C. unchanged.
B
80. ______________ is the universal energy carrier. A. Glucose B. ATP C. ADP D. GTP
B
88. NAD is derived from the vitamin A. B-12, cobalamin. B. B-3, niacin. C. B-2, riboflavin. D. B-6, pyridoxine
B
90. Chemically reduced FAD has __________ extra hydrogen atom(s) bound to it. A. one B. two C. three D. no
B
92. If NAD becomes reduced it is a(n) A. reducing agent. B. oxidizing agent. C. zymogen. D. allosteric inhibitor.
B
48. ______________ are inactive forms of digestive enzymes. A. Cofactors B. Coenzymes C. Zymogens D. Both cofactors and zymogens are correct.
C
52. Addition of substrate when enzyme reaction rate is maximal results in A. additional product formation. B. less product formation. C. no change in product formation. D. enzyme destruction.
C
60. In response to increased concentration of the final product of a metabolic pathway A. all enzymes in the pathway become more active. B. intermediate enzymes become more active. C. the final product acts as an allosteric regulator of one enzyme in the pathway. D. all enzymes in the pathway become less active.
C
69. The flow of energy in living systems is termed A. entropy. B. enthalpy. C. bioenergetics. D. bioluminescence
C
78. A food calorie (Calorie) is equivalent to which metric measurement of heat? A. calorie B. joule C. kilocalorie D. watt
C
81. In bioenergetic pathways, as intermediates are acted upon by enzymes, the ultimate result is the release of A. lactate. B. ATP. C. free energy. D. enzymes.
C
89. FAD is derived from vitamin A. B-12. B. B-3, niacin. C. B-2, riboflavin. D. B-6.
C
97. A common reducing agent used to couple chemical reactions in cells is A. riboflavin. B. niacin. C. NADH. D. FAD.
C
56. Regulation of a metabolic pathway by the final product of the pathway is termed A. allosteric inhibition. B. end-product inhibition. C. negative feedback. D. Both end-product inhibition and negative feedback are correct.
D
64. Metal ions such as magnesium or calcium can serve as enzyme A. coenzymes. B. ribozymes. C. substrates. D. cofactors.
D
77. A ______________ is the amount of heat required to raise the temperature of one cubic centimeter of water one degree on the Celsius scale. A. specific heat B. meter C. boiling point D. calorie
D
93. During oxidation, a molecule or atom A. gains protons. B. loses protons. C. gains electrons. D. loses electrons.
D
96. A common oxidizing agent used to couple chemical reactions in cells is A. riboflavin. B. niacin. C. NADH. D. FAD.
D
95. A reducing agent A. donates protons to an atom or molecule. B. donates electrons to an atom or molecule. C. accepts protons from an atom or molecule. D. accepts electrons from an atom or molecule. E. Both donates electrons and donates protons are correct.
E
37. The pH optimum for enzymes secreted by the stomach is higher than the pH optimum for enzymes secreted by the pancreas.
FALSE
38. The pH optima for all digestive enzymes are approximately equal to the pH of blood.
FALSE
47. Active enzymes are often called zymogens.
FALSE
50. The principle that reversible reactions will be driven from the side of the equation where the concentration is lower to the side where the concentration is higher is known as the law of mass action.
FALSE
53. Most enzymatic reactions in the body are one step processes.
FALSE
54. Enzymes in a metabolic pathway act antagonistically to produce a final product.
FALSE
79. The reaction of adenosine diphosphate and phosphate generates adenosine triphosphate and energy.
FALSE
84. Oxidation means that oxygen is part of the reaction.
FALSE
86. A molecule that gains a hydrogen is also oxidized.
FALSE
9. An enzyme-catalyzed reaction in the body at 50C will proceed at a faster rate than at 37C.
FALSE
99. Consuming extra niacin and riboflavin in the diet will provide extra energy for body functions.
FALSE
13. Enzymes are specific for a given substrate.
TRUE
23. Pyruvate dehydrogenase catalyzes the removal of hydrogen from pyruvic acid.
TRUE
24. The conversion of glucose to galactose is catalyzed by an isomerase.
TRUE
28. The MM isoenzyme of creatine phosphokinase is found in diseased skeletal muscle.
TRUE
3. In some instances RNA can act as an enzyme.
TRUE
36. In general, decreased body temperature causes the rate of enzymatic reactions to decrease.
TRUE
4. During a chemical reaction, a catalyst increases the rate at which the reaction occurs.
TRUE
43. Coenzymes are organic molecules that are required for proper function of some enzymes.
TRUE
44. A deficiency of dietary copper could limit the activity of some enzymes.
TRUE
5. Catalysts increase reaction rates by lowering the activation energy of a reaction.
TRUE
55. End-product inhibition usually involves allosteric inhibition of an enzyme.
TRUE
65. Free energy is the only type that can be used to perform cellular work.
TRUE
66. The amount of entropy increases as bonds are broken to generate glucose from glycogen.
TRUE
72. Another name for the first law of thermodynamics is the law of conservation of energy.
TRUE
74. Exergonic reactions proceed with the release of energy.
TRUE
82. Oxidizing agents accept electrons from molecules undergoing reduction.
TRUE
83. A reducing agent donates electrons to a molecule.
TRUE
85. An atom or molecule that is oxidized is also a reducing agent.
TRUE
87. Reduction and oxidation are always coupled.
TRUE
11. The process that yeast uses to make alcohol from glucose is A. fermentation. B. aerobic respiration. C. photosynthesis. D. catalysis.
a
20. Elevated plasma aldolase could be indicative of A. muscular dystrophy. B. pancreatitis. C. pernicious anemia. D. prostate cancer.
a
22. Reactant molecules of enzyme action are called A. substrates. B. allosteric inhibitors. C. cofactors. D. products.
a
10. Which of the following statements about enzymes is NOT true? A. Enzymes increase chemical reaction rates. B. Enzymes are consumed during a chemical reaction. C. Enzymes decrease the free energy of activation of specific reactions. D. Enzymes have unique pH and temperature optima.
b
18. The level of protein structure primarily involved in determining enzyme activity is the A. primary structure. B. secondary structure. C. tertiary structure. D. quaternary structure.
c
2. Which of the following is NOT a characteristic of a catalyst? A. is not changed itself at the end of the reaction B. does not change the nature of the reaction C. can change the final result of the reaction D. increases the rate of the reaction
c
6. Ribozymes are RNA molecules that act as A. hormones. B. cofactors. C. enzymes. D. inhibitors.
c
14. The substrate binds to the ______________ of the enzyme. A. allosteric site B. acidic site C. neutral site D. active site
d
17. An enzyme elevated in the plasma of men with prostate cancer is A. alkaline phosphatase. B. catalase. C. creatine kinase. D. acid phosphatase.
d