Biochem Chapter 13 EXAM13
1. All are distinctive features of enzymes EXCEPT:
a. regulation.
b. catalytic activity.
c. ability to change ΔG.
d. specificity.
e. none is true. - CORRECT ANSWER-C
2. Enzymes work by: - CORRECT ANSWER-c. lowering the activation energy of the
reaction
3. Which of the following statements is true regarding enzyme pathways? Acting in
sequence, enzymes form ____________ and situated at key junctions are specialized
___________ enzymes capable of sensing the momentary metabolic needs and
adjusting their ___________ rates accordingly. - CORRECT ANSWER-d. metabolic
pathways are necessary since enzymes usually catalyze only one specific reaction
4. If the rate constant for the enzyme catalyzed reaction is 2 X 10^5/sec and the rate
constant for the uncatalyzed reaction is 2 X 10^-6/sec, the catalytic power of the
enzyme is: - CORRECT ANSWER-10^11
5. An enzyme's specificity can be due to: - CORRECT ANSWER-b. molecular
recognition based on structural complementarity.
6. The specific site on the enzyme where __________ binds and catalysis occurs is
called the _____________ site. - CORRECT ANSWER-b. substrate; active
7. The trivial term for an enzyme that is an ATP-dependent phosphotransferase is a(n):
- CORRECT ANSWER-d. kinase
8. All of the following are properties of a coenzyme EXCEPT:
a. They are usually actively involved in the catalytic reaction of the enzyme.
b. They tend to be stable to heat.
c. They can serve as intermediate carriers of functional groups.
d. They are protein components.
e. They may contain vitamins as part of their structure. - CORRECT ANSWER-D
9. The catalytically active complex of an apoenzyme and its prosthetic group is referred
to a(n) _______________. - CORRECT ANSWER-b. holoenzyme
10. What reaction would NOT proceed via bimolecular elementary steps?
a. C + D → T + U
b. A reaction with a rate constant in the units of s-1.
, c. 2A → D + E
d. A reaction with a molecularity of 2. - CORRECT ANSWER-B
11. The free energy of activation, ΔG‡, is defined as: - CORRECT ANSWER-c. The
energy required to raise the average energy of one mole of reactant to the transition
state energy.
12. All of the following are true statements about the transition state of a reaction
EXCEPT:
a. The transition state is not an appropriate indication of the rate of a reaction.
b. The transition state is located at the height of a free energy diagram.
c. The energy required to raise the average energy of one mole of reactant to the
transition state is the free energy of activation.
d. Reaching the transition state indicates that there is a high probability that the reaction
will occur.
e. The transition state energy level is the sum of the energy levels of the reactants and
products. - CORRECT ANSWER-C
13. How do catalysts work to accelerate a chemical reaction? - CORRECT ANSWER-c.
They lower the energy of activation.
14. All are true for catalysts EXCEPT:
a. They work by lowering the energy of activation.
b. The average energy of the reaction is unchanged.
c. They combine transiently with the reactants promoting a reactive transition state
condition.
d. They are regenerated after each reaction cycle.
e. All are true. - CORRECT ANSWER-E
15. When every enzyme molecule in the reaction mixture has its substrate-binding site
occupied by substrate, the kinetics become _________-order, and the velocity is
______________. - CORRECT ANSWER-a. zero; Vmax
16. Which of the following is true regarding the Briggs and Haldane steady state
assumption? - CORRECT ANSWER-c. The concentration of the enzyme-substrate
complex reaches a constant value even in a dynamic system.
17. Which statement is correct about the Michaelis-Menten constant, Km, for the kinetic
mechanism below?
k1 k2
E + S ↔ ES → E + P
k-1 - CORRECT ANSWER-a. It is numerically equal to the substrate concentration
required to achieve one half the maximum velocity.
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