763 / 912
Chapter 22 755
Copyright © 2017 Pearson Education, Inc.
Chapter 22 Practice Test
1.
Indicate whether each of the following statements is true or false:
a.
A catalyst increases the equilibrium constant of a reaction.
T
F
b.
An acid catalyst donates a proton to the substrate, and a base catalyst
removes a proton from the substrate.
T
F
c.
The reactant of an enzyme-catalyzed reaction is called a substrate.
T
F
d.
Complexing with a metal ion increases the p
K
a
of water.
T
F
2.
In lysozyme, glutamate 35 is a catalyst that is active in its acid form. Explain its catalytic function.
3.
a.
Draw a pH-rate profile for an enzyme that has one catalytic group at the active site with a p
K
a
=
5.7
that functions as a general-base catalyst.
b.
Draw a pH-rate profile for an enzyme that has one catalytic group at the active site with a p
K
a
=
5.7
that functions as a general-acid catalyst.
4.
Show the curved mechanism arrows for the first step in the mechanism for chymotrypsin.
−
−
+
−
His
O
O
Asp CH CO HN N
HN NH
Ser
CH
O
H
R
C O
NHR
rst step
195
Ser
195
2
CH
R
O
OC
NHR
2
CH
57
His
57
102
Asp
102
2
CH CO
2
2
CH
2
a.
What kind of catalyst is histidine in this step?
b.
What kind of catalyst is serine in this step?
c.
How does aspartate catalyze the reaction?