1
Q1.Which of the following is true?
1)
Enzymes force reactions to proceed in only one direction.
2)
Enzymes alter the equilibrium of the reaction.
3)
Enzymes alter the standard free energy of the reaction.
4)
All of the above.
5)
None of the above.
Q2. When substrate concentration is much greater than Km, the rate of catalysis is almost
equal to
1) Kd.
2) kcat.
3) Vmax.
4) All of the above.
5) None of the above.
Q3. If you carried out sitedirected mutagenesis of chymotrypsin, changing serine 195 to
isoleucine, what would you expect?
1)
a large change in
K
M
4)
1 and 3
2)
a small change in
K
M
5)
2 and 3
3)
a large change in
k
cat
Q4.
Which of the following statements about a plot of
V
0
vs. [S] for an enzyme that follows
MichaelisMenten kinetics is
false
?
1)
As [S] increases, the initial velocity of reaction
V
0
also increases.
2)
At very high [S], the velocity curve becomes a horizontal line that intersects the yaxis at
K
m
.
3)
K
m
is the [S] at which
V
0
= 1/2
V
max
.
4)
The shape of the curve is a hyperbola.
5)
The yaxis is a rate term with units of μm/min.
Q5.
Michaelis and Menten assumed that the overall reaction for an enzymecatalyzed reaction
could be written as
k
1
k
2
E + S
ES
E + P
k
1
Using this reaction, the rate of breakdown of the enzymesubstrate complex can be described by the
expression:
1)
k
1
([E
t
] [ES]).
2)
k
1
([E
t
] [ES])[S].
3)
k
2
[ES].
4)
k
1
[ES] +
k
2
[ES].
5)
k
1
[ES].
Q6.
For an enzymatic reaction obeying the Michaelis–Menten equation to reach 3/4 its
maximum velocity (perhaps a useful hint:
what happens when you set v
o
= Vmax/2),
1)
[S] would need to be 2
K
M
2) not enough information is given to make this calculation
3)
[S] would need to be 50% greater than
K
M
4) [S] would need to be 3
K
M
5) [S] would need to be 3/4
K
M
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Q7. Fructose (a ketohexose) can cyclize to (a)
1)
pyranose ring.
2)
furanose ring.
3)
both pyranose and furanose ring forms.
4)
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 Fall '08
 LSPREMULLI
 Enzymes, Glucose, Glycolysis, Enzyme, Reaction, Adenosine triphosphate

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