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7. Enzyme Inhibition and Regulation

1

Apparent Km and Vmax

2m

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2

Apparent Km and Vmax

7m

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3

Apparent Km and Vmax Example 1

3m

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4

Problem

Competitive inhibitor A at a concentration of 2 μM doubles the apparent K _{m} for an enzymatic reaction, whereas competitive inhibitor B at a concentration of 9 μM quadruples the apparent K_{m}. What is the ratio of the K _{I} for inhibitor B to the K _{I} for inhibitor A?

A

1.5

B

3

C

4

D

2/3

E

1/4

5

Problem

The K_{I} value for a certain competitive inhibitor is 10 mM. When no inhibitor is present, the K_{m} value is 50 mM. Calculate the apparent K_{m} when 40 mM inhibitor is present.

A

20 mM.

B

10 mM.

C

100 mM.

D

150 mM.

E

250 mM.

6

Problem

Uncompetitive inhibitor A at a concentration of 4 mM cuts the K _{m}^{app} in half for an enzymatic reaction, whereas the K_{m}^{app} is one-fourth the K_{m} in the presence of 18 mM uncompetitive inhibitor B. What is the ratio of the K’_{I} for inhibitor A to the K’_{I} for inhibitor B?

A

3/2

B

2/3

C

1/3

D

3

E

1