ACS Biochemistry Practice Final, FGCU, Beharry,
Coticone Questions with verified answers
1. A weak acid, HA, has a pKa of 4.11.
a) At pH 7.11, what will the ratio of conjugate base to acid be? (Henderson-
Hasselbach equation: pH=pKa + log [A-]/[HA])
b) Based on answer to "a," is there more HA or A- at that pH?
c) At pH 2.11, what will the ratio of conjugate base to acid be?
d) Based on answer to "c," is there more HA or A- at that pH?
e) At pH 4.11, what will the ratio of conjugate base to acid be?
f) Fill in the blank: if pH is greater than the pKa of a weak acid, there will be ___ A-
relative to HA. If the pH is less that the pKa of a weak acid, there will be __ A-
relative to HA. If the pH=pKa, there will be ___ of A- and HA. Ans✓✓✓ a)
7.11=4.11+log[x]
3=log[x]
1000=x
b) A-
c) 2.11=4.11+log[x]
-2=log[x]
0.01=x
d) HA
e) 1
f) more; less; the same amount
10.
a) graph
, b) which trace (solid or dashed) represents an uncatalyzed reaction?
c) based on "b", what effect does enzyme have on deltaG?
d) based on "b", what effect does enzyme have on the transition state as far as
reaching it and stabilizing it? Ans✓✓✓ a) graph
b) solid = uncatalyzed, dashed = catalyzed
c) none
d) makes it easier to get to but does not stabilize it
11. In the enzyme mechanism below, follow the arrows to label the function of
H2O, the carbonyl, Asp32, and Asp215. Your choices are electrophile, nucleophile,
base, and acid. Make sure you use each one. Ans✓✓✓ see graph
12. Arginase is part of the urea cycle, catalyzing the hydrolysis of arginine to urea
and ornithine. It is also a target for drug development. It is thought that inhibiting
it might be a treatment for asthma. Two transitions state inhibitors are shown
(see skematic)
a) what is a transition state inhibitor (how does its structure compare to the
enzyme substrate? how does its affinity for the enzyme compare to the enzyme's
substrate?)?
b) Would it be advantageous for these potential drugs to covalently bind to the
enzyme? why/why not?
c) from a practical standpoint, would it be advantageous for these potential drugs
to be less chemically stable than the substrate? Ans✓✓✓ a) similar to the
substrate; binds to the active site with greater affinity than the substrate
b) not advantageous because the urea cycle would shut down
c) no, because shelf life and time to reach target
13.
Coticone Questions with verified answers
1. A weak acid, HA, has a pKa of 4.11.
a) At pH 7.11, what will the ratio of conjugate base to acid be? (Henderson-
Hasselbach equation: pH=pKa + log [A-]/[HA])
b) Based on answer to "a," is there more HA or A- at that pH?
c) At pH 2.11, what will the ratio of conjugate base to acid be?
d) Based on answer to "c," is there more HA or A- at that pH?
e) At pH 4.11, what will the ratio of conjugate base to acid be?
f) Fill in the blank: if pH is greater than the pKa of a weak acid, there will be ___ A-
relative to HA. If the pH is less that the pKa of a weak acid, there will be __ A-
relative to HA. If the pH=pKa, there will be ___ of A- and HA. Ans✓✓✓ a)
7.11=4.11+log[x]
3=log[x]
1000=x
b) A-
c) 2.11=4.11+log[x]
-2=log[x]
0.01=x
d) HA
e) 1
f) more; less; the same amount
10.
a) graph
, b) which trace (solid or dashed) represents an uncatalyzed reaction?
c) based on "b", what effect does enzyme have on deltaG?
d) based on "b", what effect does enzyme have on the transition state as far as
reaching it and stabilizing it? Ans✓✓✓ a) graph
b) solid = uncatalyzed, dashed = catalyzed
c) none
d) makes it easier to get to but does not stabilize it
11. In the enzyme mechanism below, follow the arrows to label the function of
H2O, the carbonyl, Asp32, and Asp215. Your choices are electrophile, nucleophile,
base, and acid. Make sure you use each one. Ans✓✓✓ see graph
12. Arginase is part of the urea cycle, catalyzing the hydrolysis of arginine to urea
and ornithine. It is also a target for drug development. It is thought that inhibiting
it might be a treatment for asthma. Two transitions state inhibitors are shown
(see skematic)
a) what is a transition state inhibitor (how does its structure compare to the
enzyme substrate? how does its affinity for the enzyme compare to the enzyme's
substrate?)?
b) Would it be advantageous for these potential drugs to covalently bind to the
enzyme? why/why not?
c) from a practical standpoint, would it be advantageous for these potential drugs
to be less chemically stable than the substrate? Ans✓✓✓ a) similar to the
substrate; binds to the active site with greater affinity than the substrate
b) not advantageous because the urea cycle would shut down
c) no, because shelf life and time to reach target
13.
