Biochemical reactions in cells are controlled by enzymes: Practice Questions

In the induced fit model of enzyme action, how does the active site interact with the substrate molecule?

A reaction was carried out with a limiting concentration of substrate. When more enzyme was added to the mixture, the initial rate of reaction increased, but the total amount of product formed remained the same. Why did the total amount of product not increase?

An enzyme-controlled reaction is inhibited by a molecule that binds to a site other than the active site. This binding distorts the tertiary structure of the enzyme. What type of inhibition is occurring?

Which of the following best describes the effect of a non-competitive inhibitor on the kinetics of an enzyme-controlled reaction?

Which of the following statements correctly explains how enzymes increase the rate of biochemical reactions?

How does a non-competitive inhibitor reduce the rate of an enzyme-controlled reaction, and why does increasing the substrate concentration fail to overcome its effect?

The rate of an enzyme-controlled reaction changes significantly with temperature.

a) Explain why an increase in temperature up to the optimum increases the rate of reaction in terms of kinetic energy and collisions.
b) Beyond the optimum temperature, the rate of reaction decreases rapidly. Describe the changes occurring in the tertiary structure of the enzyme that lead to this decrease and explain why the substrate can no longer bind.

The effect of pH on enzyme activity is related to the charges on the amino acids making up the active site.

a) Explain how a change in pH away from the optimum can lead to the denaturation of an enzyme.
b) Describe how extreme pH values interfere specifically with ionic bonds within the protein structure.
c) Even a small change in pH that does not fully denature the enzyme can still reduce the rate of reaction. Suggest how this might affect the attraction between the active site and the substrate.