a. 1
b. 7
c. 10
d. 13
Ans: c
Question Type: Multiple Choice
Chapter: 2
Blooms: Applying
Difficulty: Moderate
24. The pKa of the weak base NH3 is 9.25. When present in lysosomes, a subcellular organelle—ammonia—is almost totally protonated. Which of the pH values listed below is most likely to be that of the lysosome lumen?
a. 1
b. 5
c. 8
d. 14
Ans: b
Question Type: Multiple Choice
Chapter: 2
Analysis
Difficulty: Difficult
25. If the equilibrium constant for the reaction A ® B is 0.5 and the initial concentration of A is 25 mM and of B is 12.5 mM, then the reaction:
a. will proceed in the direction it is written, producing a net increase in the concentration of B.
b. will produce energy, which can be used to drive ATP synthesis.
c. will proceed in the reverse direction, producing a net increase in the concentration of A.
d. is at equilibrium.
Ans: d
Question Type: Multiple Choice
Chapter: 2
Analysis
Difficulty: Difficult
26. For the binding reaction A + B ® AB, the dissociation constant is equal to:
a. [AB]/([A] + [B]).
b. ([A] + [B])/[AB].
c. Keq
d. The first and third answers are correct.
Ans: b
Question Type: Multiple Choice
Chapter: 2
Blooms: Applying
Difficulty: Easy
27. What is the effect of an enzyme on the end equilibrium concentration of reactants and products?
Ans: An enzyme has no effect on the end equilibrium concentration of reactants and products.
Question Type: Essay
Chapter: 2
Blooms: Analyzing
Difficulty: Easy
28. The enzyme alcohol dehydrogenase is capable of catalyzing the oxidation of a number of different substances, including ethanol, ethylene glycol, and methanol, to an aldehyde. The metabolic products of both ethylene glycol and methanol are highly toxic to humans. A standard medical treatment for prevention of ethylene glycol or methanol poisoning is the administration of a dose of ethanol. Why is this treatment effective?
Ans: The ethanol-like ethylene glycol and methanol are capable of binding to the enzyme, alcohol dehydrogenase, and competing with its other substrates. A sufficient dosage of ethanol can out-compete the other substrates, and hence the ethylene glycol and methanol are not metabolized to toxic products. Gradually the ethylene glycol or methanol will be excreted from the body.
Question Type: Essay
Chapter: 2
Blooms: Evaluating
Difficulty: Moderate
29. How do cells maintain a relatively constant pH despite the fact that many metabolic processes produce acids?
Ans: All cells contain buffers such as phosphate ions that can absorb or release protons or hydroxyl ions to stabilize pH changes near neutral pH.
Question Type: Essay
Chapter: 2
Blooms: Evaluating
Difficulty: Difficult
Section 2.4
30. In a biochemical reaction in which DH < 0 and DS > 0:
a. the reaction is spontaneous.
b. the reaction is endothermic.
c. the reaction is endergonic.
d. DG is positive.
Ans: a
Question Type: Multiple Choice
Chapter: 2
Blooms: Applying
Difficulty: Easy
31. In the reaction NAD+ + H+ + 2e− ® NADH, NAD+ becomes:
a. dehydrated.
b. hydrolyzed.
c. oxidized.
d. reduced.
Ans: d
Question Type: Multiple Choice
Chapter: 2
Blooms: Understanding
Difficulty: Easy
32. The ultimate source of chemical energy for all cells is:
a. electricity.
b. heat.
c. light.
d. magnetism.
Ans: c
Question Type: Multiple Choice
Chapter: 2
Blooms: Applying
Difficulty: Moderate
33. Hydrolysis of ATP:
a. is endothermic.
b. has a positive G value.
c. must be coupled to an energetically favorable reaction.
d. none of the above
Ans: d
Question Type: Multiple Choice
Chapter: 2
Blooms: Understanding
Difficulty: Easy
34. What is [P]/[R] when DG =DG°´?
a. –1
b. 0
c. 1
d. 2.3
Ans: c
Question Type: Multiple Choice
Chapter: 2
Blooms: Applying
Difficulty: Moderate
35. A reaction with a positive DG value can be made energetically favorable by increasing the:
a. DG°¢.
b. starting concentration of products.