This preview shows pages 1–3. Sign up to view the full content.
Kaiser Imam
September 23, 2007
BIOL 215 Exam 1 Review
Enzyme Kinetics
1.
Why does v
max
but not K
m
depend on the amount of enzyme used in an enzyme reaction?
The velocity equation for v
max
includes the concentration of enzyme (actually, the
concentration of enzyme
active sites
):
v
max
= k
2
[E] = k
cat
[E]; K
m
is a substrate
concentration and is independent of the concentration of enzyme.
2.
Write out the direct kinetic function.
v
o
=
___V
max
[S]
____
[S]
+
K
m
3.
The following data were obtained by measuring the change in reaction rate in an enzyme
catalyzed reaction over time.
The k
cat
for the enzyme is known to be 1500 min
1
.
Find the
K
m
and the total enzyme concentration value from the data below:
[S] (mM)
v
o
(μmol/min)
1.00
49
2.00
96
8.00
349
50.00
621
100.00
676
1000.00
698
5000.00
699
In this situation v
max
would be about 700, so therefore ½ v
max
would be 349.
The
corresponding [S] for that v
o
value is 8 M.
Therefore, the K
m
value is 8 mM.
To find the
enzyme concentration use the equation
v
max
= k
cat
[E]: v
max
= 700, k
cat
= 1500
[E] = v
max
/ k
cat
= 700/1500 = 0.47 µmol.
4.
What is the equation for the LineweaverBurk plot and what does it tell you?
The direct kinetic plot has limitations since it depends on how accurately one can
estimate the v
max
(the asymptote value).
The LineweaverBurk plot, also called the
double reciprocal plot, can be found by rearranging the direct kinetic function.
1/ v
o
=
1/ v
max
+
(K
m
/v
max
) (1 / [S])
The LineweaverBurk plot allows us to find K
m
and v
max
more accurately than the direct
kinetic function.
1
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
For a onesubstrate, enzymecatalyzed reaction LineweaverBurk plots were determined
for
three different enzyme concentrations
.
Which of the following three sets of plots
would best describe this situation?
The family of curves in b) would be expected to be obtained.
If the total amount of
enzyme ([E]) is increased, v
max
will increase since v
max
= k
cat
[E].
But remember that K
m
is
unaffected by changes in enzyme concentration.
Therefore, you should look for plots
that show changes in v
max
without changes in K
m
, as is shown in b).
6.
What is the equation for the EadieHofstee plot?
The EadieHofstee graph plots (v
o
/[S]) against v
o
.
The equation for the EadieHofstee
plot is
v
o
/ [S]
=
(v
max
/K
m
)

(1/K
m
) v
o
7.
What are the three types of inhibition?
1)
Competitive: inhibitor and substrate compete for binding directly to the active site
2)
Uncompetitive: inhibitor binds to an allosteric site only, making it more difficult for
the substrate to bind to the active site
3)
Noncompetitive: also called mixed inhibition; inhibitor binds in either of the forms
described above
8.
Modify the MichaelisMenten mechanism to explain the various types of reversible
inhibition and describe which type of inhibition is occurring in each.
E
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '09
 DiIulio

Click to edit the document details