Enzyme Kinetics and Inhibition

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Biochemistry › Enzyme Kinetics and Inhibition

Questions 1 - 10
1

If an enzymatic reaction is interrupted by the presence of a non-competitive inhibitor, which of the following best describes how the reaction kinetics will be effected?

Only will be decreased

Only will be increased

Only will decrease

Both and decrease

decreases but increases

Explanation

Non-competitive inhibitors work by binding the enzyme without hindering the substrate's access to the active site. Therefore, the affinity of the enzyme to its substrate is not impacted , however it does negatively impact the enzyme's ability to form the final product. Therefore, the maximum velocity of the reaction is decreased.

2

Upon analysis, it is determined that the interaction between an inhibitor and an enzyme involves the formation of bonds between nitrogen and hydrogen atoms in adjacent molecules. Which of the following is true regarding this molecule?

More than one of these

It binds to the allosteric site of the enzyme

Its effects can be overcome by increasing substrate concentration

It decreases the affinity between the substrate and enzyme

Explanation

The question states that the bond between nitrogen and hydrogen atoms occur between adjacent molecules; therefore, this is an intermolecular bond. Recall that hydrogen bonds are intermolecular bonds that occur between hydrogen atoms and either nitrogen, oxygen, or fluorine atoms. This means that the intermolecular bond involved in this question is a hydrogen bond. Hydrogen bonds (like other intermolecular bonds) are reversible and can be broken by applying some energy. Since the bond between the inhibitor and the enzyme is reversible, the inhibitor must be a competitive inhibitor. Noncompetitive inhibitors, on the other hand, bind irreversibly (via covalent bonds) to the allosteric site on the enzyme.

Competitive inhibitors can be overcome by increasing substrate concentration. This occurs because the reversible, weak bonds between the inhibitor and enzyme can be broken when there is excess substrate present (substrate competes with the competitive inhibitors for the enzyme). Competitive inhibitors also increase the Michaelis-Menton constant, . Increasing decreases affinity between substrate and enzyme.

3

If an enzymatic reaction is interrupted by the presence of a non-competitive inhibitor, which of the following best describes how the reaction kinetics will be effected?

Only will be decreased

Only will be increased

Only will decrease

Both and decrease

decreases but increases

Explanation

Non-competitive inhibitors work by binding the enzyme without hindering the substrate's access to the active site. Therefore, the affinity of the enzyme to its substrate is not impacted , however it does negatively impact the enzyme's ability to form the final product. Therefore, the maximum velocity of the reaction is decreased.

4

If an enzymatic reaction is interrupted by the presence of a non-competitive inhibitor, which of the following best describes how the reaction kinetics will be effected?

Only will be decreased

Only will be increased

Only will decrease

Both and decrease

decreases but increases

Explanation

Non-competitive inhibitors work by binding the enzyme without hindering the substrate's access to the active site. Therefore, the affinity of the enzyme to its substrate is not impacted , however it does negatively impact the enzyme's ability to form the final product. Therefore, the maximum velocity of the reaction is decreased.

5

Upon analysis, it is determined that the interaction between an inhibitor and an enzyme involves the formation of bonds between nitrogen and hydrogen atoms in adjacent molecules. Which of the following is true regarding this molecule?

More than one of these

It binds to the allosteric site of the enzyme

Its effects can be overcome by increasing substrate concentration

It decreases the affinity between the substrate and enzyme

Explanation

The question states that the bond between nitrogen and hydrogen atoms occur between adjacent molecules; therefore, this is an intermolecular bond. Recall that hydrogen bonds are intermolecular bonds that occur between hydrogen atoms and either nitrogen, oxygen, or fluorine atoms. This means that the intermolecular bond involved in this question is a hydrogen bond. Hydrogen bonds (like other intermolecular bonds) are reversible and can be broken by applying some energy. Since the bond between the inhibitor and the enzyme is reversible, the inhibitor must be a competitive inhibitor. Noncompetitive inhibitors, on the other hand, bind irreversibly (via covalent bonds) to the allosteric site on the enzyme.

Competitive inhibitors can be overcome by increasing substrate concentration. This occurs because the reversible, weak bonds between the inhibitor and enzyme can be broken when there is excess substrate present (substrate competes with the competitive inhibitors for the enzyme). Competitive inhibitors also increase the Michaelis-Menton constant, . Increasing decreases affinity between substrate and enzyme.

6

Upon analysis, it is determined that the interaction between an inhibitor and an enzyme involves the formation of bonds between nitrogen and hydrogen atoms in adjacent molecules. Which of the following is true regarding this molecule?

More than one of these

It binds to the allosteric site of the enzyme

Its effects can be overcome by increasing substrate concentration

It decreases the affinity between the substrate and enzyme

Explanation

The question states that the bond between nitrogen and hydrogen atoms occur between adjacent molecules; therefore, this is an intermolecular bond. Recall that hydrogen bonds are intermolecular bonds that occur between hydrogen atoms and either nitrogen, oxygen, or fluorine atoms. This means that the intermolecular bond involved in this question is a hydrogen bond. Hydrogen bonds (like other intermolecular bonds) are reversible and can be broken by applying some energy. Since the bond between the inhibitor and the enzyme is reversible, the inhibitor must be a competitive inhibitor. Noncompetitive inhibitors, on the other hand, bind irreversibly (via covalent bonds) to the allosteric site on the enzyme.

Competitive inhibitors can be overcome by increasing substrate concentration. This occurs because the reversible, weak bonds between the inhibitor and enzyme can be broken when there is excess substrate present (substrate competes with the competitive inhibitors for the enzyme). Competitive inhibitors also increase the Michaelis-Menton constant, . Increasing decreases affinity between substrate and enzyme.

7

Which of the following is true about noncompetitive inhibition?

The inhibitor binds independently of substrate binding however km does not change

The inhibitor binds to the same site as the substrate, dropping the Km

The inhibitor competes with the substrate to bind to the active site, and drops the Vmax

The inhibitor binds to a separate site from the substrate and enhances enzyme activity

Vmax stays the same, however Km increases

Explanation

With uncompetitive inhibitors, the inhibitor binds to a site separate from the binding site of the substrate. This can occur even while the substrate is bound to the enzyme, blocking the process and reduce the catalysis of the enzyme.

This will result in the reduction of Vmax because the enzymes ability for catalysis is being reduced by the binding of inhibitor to the enzyme-substrate complex. Km does not change because the substrate and the uncompetitive inhibitor bind to different sites.

8

Which of the following is true about noncompetitive inhibition?

The inhibitor binds independently of substrate binding however km does not change

The inhibitor binds to the same site as the substrate, dropping the Km

The inhibitor competes with the substrate to bind to the active site, and drops the Vmax

The inhibitor binds to a separate site from the substrate and enhances enzyme activity

Vmax stays the same, however Km increases

Explanation

With uncompetitive inhibitors, the inhibitor binds to a site separate from the binding site of the substrate. This can occur even while the substrate is bound to the enzyme, blocking the process and reduce the catalysis of the enzyme.

This will result in the reduction of Vmax because the enzymes ability for catalysis is being reduced by the binding of inhibitor to the enzyme-substrate complex. Km does not change because the substrate and the uncompetitive inhibitor bind to different sites.

9

Which of the following is true about noncompetitive inhibition?

The inhibitor binds independently of substrate binding however km does not change

The inhibitor binds to the same site as the substrate, dropping the Km

The inhibitor competes with the substrate to bind to the active site, and drops the Vmax

The inhibitor binds to a separate site from the substrate and enhances enzyme activity

Vmax stays the same, however Km increases

Explanation

With uncompetitive inhibitors, the inhibitor binds to a site separate from the binding site of the substrate. This can occur even while the substrate is bound to the enzyme, blocking the process and reduce the catalysis of the enzyme.

This will result in the reduction of Vmax because the enzymes ability for catalysis is being reduced by the binding of inhibitor to the enzyme-substrate complex. Km does not change because the substrate and the uncompetitive inhibitor bind to different sites.

10

What does a small indicate?

That the enzyme requires only a small amount of substrate to become saturated

That the enzyme requires a large amount of substrate to become saturated

That high substrate concentrations are needed to achieve maximum reaction velocity

The enzyme has a low affinity for its substrate

Explanation

In enzyme kinetics, is the concentration of substrate which allows the enzyme to reach (maximum reaction velocity). A small indicates that only a small amount of substrate is needed for the enzyme to become saturated and thus for the reaction to reach maximum velocity. This also indicates that the enzyme and substrate have high affinity for one another. A large indicates that a large amount of substrate is needed for the enzyme to become saturated and thus for the reaction to reach maximum velocity.

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