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1. The sum total of all the chemical reactions in a living structure is called its
2. Water held back by a dam represents what kind of energy?
3. Which of the following represents potential energy?
a. Chemical bonds
b. Concentration gradient
c. Electric charge imbalance
4. What can never be created or destroyed?
5. During photosynthesis, plants use light energy to synthesize glucose from carbon dioxide. However, plants do not use up energy during photosynthesis; they merely convert it from light energy to chemical energy. This process is an illustration of
c. the first law of thermodynamics.
6. The first law of thermodynamics states that the total energy in the universe is
7. In any system, the total energy includes usable and unusable energy. The unusable energy is a measure of the disorder of the system and is referred to as
8. A change in free energy is related to a change in
a. temperature.b. entropy
9. If DG of a chemical reaction is negative and the change in entropy is positive, you can conclude that the reaction
c. is exergonic.
10. The standard free energy change for the hydrolysis of ATP to ADP + Pi is –7.3 kcal/mol. From this information one can conclude that
e. the reaction is exergonic.
11. Which of the following statements about the exergonic hydrolysis of maltose to glucose is true?
d. The reaction releases free energy.
12. Chemical equilibrium
e. is a state in which DG = 0.
13. When ADP gains a phosphate to form ATP,
b. energy is consumed.
14. How does the second law of thermodynamics apply to organisms?
b. To maintain order, life requires a constant input of energy.
16. ATP can phosphorylate many different molecules. This means that ATP can
b. donate phosphate groups.
17. A readily reversible reaction, in which reactants and products have almost the same free energies, is indicated by a
d. DG near zero.
18. Phosphorylation of ADP to ATP is endergonic, whereas the hydrolysis of ATP to ADP is exergonic. The two reactions are therefore said to be
19. In glycolysis, the exergonic reaction 1,3-diphosphoglycerate ® 3-phosphoglycerate is coupled to the reaction ADP + Pi ® ATP. Which of the following is most likely to be true about the reaction ADP + Pi ® ATP?
d. The reaction is endergonic.
c. use ATP to begin luciferin oxidation.
21. Which of the following statements about ATP is true?
e. On average, ATP is consumed within one second of its formation.
22. An RNA molecule that has enzyme activity is called
e. a ribozyme.
23. The rate of a chemical reaction in a cell is the measure of how
b. quickly the reaction reaches equilibrium.
24. Knowing the change in free energy (DG) of a reaction tells us
a. the equilibrium point of the reaction.
25. Which of the following is an example of an exergonic reaction?
b. Cellular respiration
26. Which of the following statements about enzymes is false?
e. Most enzymes are much smaller than their substrates.
27. What is a transition state?
d. The state at which the bonds of reactants are unstable
28. The presence of a catalyst affects the
e. free energy of the transition state.
29. Which of the following determines the rate of a reaction?
d. The activation energy
30. In a chemical reaction, transition-state species have free energies that are
b. higher than either the reactants or the products.
31. The hydrolysis of sucrose to glucose and fructose is exergonic. However, if sucrose is dissolved in water and the solution is kept overnight at room temperature, there is no detectable conversion to glucose and fructose. Why?
b. The activation energy of the reaction is high.
32. Trypsin and elastase are both enzymes that catalyze hydrolysis of peptide bonds. But trypsin only cuts next to lysine and elastase only cuts next to alanine. Why?
c. The shape of the active site for the two enzymes is different.
33. The statement “enzymes are highly specific” means that certain
b. reactions involving certain substrates are catalyzed by specific enzymes.
34. An active site is
b. the part of the enzyme that binds with a substrate.
35. In some cases, a substrate–enzyme complex is stabilized by
a. hydrogen bonds.
b. covalent bonds.
c. ionic attractions.
d. hydrophobic interactions.
36. The molecules that are acted on by an enzyme are called
37. The enzyme sucrase increases the rate at which sucrose is broken down into glucose and fructose. Sucrase works by
b. lowering the activation energy of the reaction.
38. Which of the following statements about enzymes is true?
a. Enzymes are proteins.
b. Enzymes have a specific amino acid sequence.
c. Enzymes are highly specific.
d. Enzymes lower the energy barrier.
39. The enzyme a-amylase increases the rate at which starch is broken down into smaller oligosaccharides by _______ of the reaction.
e. lowering the activation energy
40. The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction glyceraldehyde 3-phosphate ® 1,3-diphosphoglycerate. The binding of the glyceraldehyde 3-phosphate to the enzyme creates a(n)
d. enzyme–substrate complex.
41. The enzyme glucose oxidase binds the six-carbon sugar glucose and catalyzes its conversion to glucono-1,4-actone. Mannose is also a six-carbon sugar, but glucose oxidase cannot bind mannose. The specificity of glucose oxidase is based on the
d. three-dimensional shape and structure of the active site.
42. Binding of substrate to the active site of an enzyme is
43. Which of the following is an enzyme?
44. Enzymes of the acid–base catalysis type contain
d. acidic or basic amino acid side chains (R group) in the active site.
45. The catalysis mechanism used by lysozyme to breakdown bacterial cell walls is
d. induced strain.
46. Enzymes catalyze a reaction by _______ the substrates.
e. enzyme retrofit.
a. All of the alcohol dehydrogenase molecules are bound to acetaldehyde molecules.
47. The ability of an enzyme to change shape when it binds to its substrate is called
a. induced fit.
49. Many enzymes require ATP and ADP for a reaction to occur. They temporarily bind to and then release from the substrate to participate in other reactions. ATP and ADP are considered
50. Enzymatic reactions can become saturated as substrate concentration increases because
e. there are a limited number of the enzyme molecules present.
51. Competitive inhibitors of enzymes work by
a. fitting into the active site.
52. Nerve gases such as Sarin and malathion
a. block specific chemical transformations by inactivating specific enzymes.
53. How do competitive and noncompetitive enzyme inhibitors differ?
a. Competitive inhibitors bind to the active site, whereas noncompetitive inhibitors change the shape of the active site.
54. Enzymes are sensitive to
c. irreversible inhibitors such as DIPF.
d. allosteric effectors.
55. The addition of the competitive inhibitor mevinolin slows the reaction HMG-CoA ® mevalonate, which is catalyzed by the enzyme HMG-CoA reductase. The effects of mevinolin would be overcome and the rate of the reaction increased by
b. adding more HMG-CoA.
56. A noncompetitive inhibitor inhibits binding of a substrate to an enzyme by
e. changing the shape of the active site.
57. Which type of inhibitor can be overcome completely by the addition of more substrate?
58. An allosteric inhibitor
b. changes the shape of an enzyme.
59. Allosteric inhibitors act by
d. decreasing the amount of the active form of the enzyme.
60. The inhibition of enzyme activity by noncompetitive inhibitors can be reduced
e. only when they become unbound.
61. The maximum possible rate of an enzyme reaction that is influenced by a competitive inhibitor depends on the concentration of
62. Negative feedback in a sequence of chemical reactions involves a chemical that appears _______ in the sequence and _______ reaction.
a. late; inhibits an earlier
63. The process that involves an end product acting as an inhibitor of an earlier step in a metabolic pathway is called
b. feedback inhibition.
64. Which of the following statements about allosteric regulators is true?
a. The plot for allosteroic regulators often has a sigmoid curve.
65. Enzymes are highly sensitive to pH and temperature because
c. of their three-dimensional structure and side chains.
66. Environmental conditions that affect enzyme function include
67. Denatured enzymes are the same as
d. enzymes that can no longer function.
68. End products of biosynthetic pathways often act to block the initial step in that pathway. This phenomenon is called
d. feedback inhibition.
69. Which of the following is a group of enzymes that are important in allowing organisms to adapt to changes in their environment?
c. Allosteric enzymes
70. If the temperature of an enzyme-catalyzed reaction is increased from 40°C to 70°C, the rate of the reaction
e. cannot be determined without information regarding optimal temperature.
71. When organisms move from one environment to another, they sometimes synthesize variations of existing enzymes, which are called
1. Cells cannot create energy because _______ cannot be created or destroyed.
2. The capacity to do work is known as _______.
3. Heat, light, electricity, and motion are all examples of _______ energy.
4. The energy in a system that exists due to position is called _______ energy.
5. Potential energy can be converted into _______ energy, which does work.
6. The building up of molecules in a living system is known as _______; the breaking down of molecules in a living system is known as _______.
7. The first law of thermodynamics states that _______ is neither created nor destroyed.
8. The second law of thermodynamics states that the _______, or disorder, of the universe is constantly increasing.
9. When a drop of ink is added to a beaker of water, the dye molecules become randomly dispersed throughout the water. This is an example of an increase in _______.
10. If the DG of a spontaneous reaction is negative, indicating that the reaction releases free energy, the reaction is _______.
11. Cells mostly use _______ as an immediate source of energy to drive reactions.
12. Enzymes are biological _______.
13. The amount of energy needed to start a reaction is known as the _______ energy.
14. The enzyme phosphoglucoisomerase catalyzes the conversion of glucose 6-phosphate to fructose 6-phosphate. The region on phosphoglucoisomerase where glucose 6-phosphate binds is called the _______.
15. A change in enzyme shape caused by substrate binding is called _______.
16. Although some enzymes consist entirely of one or more polypeptide chains, others possess a permanently bound nonprotein portion called a(n) _______.
17. Zinc ions that bind to enzymes are called _______.
18. The chemical activities of a living organism are organized into _______ in which the product of one reaction is the reactant for the next reaction.
19. When an enzyme is heated until its three-dimensional structure is destroyed, the enzyme is said to be _______.
20. Variations of enzymes that allow organisms to adapt to changing environments are termed _______.
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