Chapter 2 : Enzymes – MyOnlineTest

Welcome to your Chapter 2 Enzymes

Which of the following statements is (are) true about enzyme catalyzed reactions?

The reaction is faster than the same reaction in the absence of enzymes

The free energy change of the reaction is opposite from the reaction in the absence of the enzyme

The reaction always goes in the direction toward chemical equilibrium.

Both a and b.

The active site of an enzyme is the region that

Binds allosteric regulators of the enzyme

Is involved in the catalytic reaction of the enzyme

Binds the products of the catalytic reaction

Is inhibited by the presence of a coenzyme or a cofactor.

According to the induced fit hypothesis of enzyme catalysis, Which of the following is correct

The binding of the substrate depends substrate depends on the shape of the active site

Some enzymes change their structure when activators bind

A competitive inhibitor can outcompete the substrate for the active site.

The binding of the subst substrate changes the shape of the enzymes active site

Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs. I. Curve 1 II. Curve 2. III. Curve 3

I only

II only

III only

I and II

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

Denaturation of the enzyme

Allosteric inhibition

Competitive inhibition

Saturation of the enzyme activity

Competitive inhibitors block the entry of substrate into the active site of an enzyme. On which of the following properties of an active site does this primarily depend?

The ability of an enzyme to form a template for holding and joining molecules

The enzyme's ability to stretch reactants and move them toward a transition state

The enzyme providing an appropriate microenvironment conduc occurrence to a reaction's

The enzyme forming covalent bonds with the reactants

A series of enzymes catalyze the reaction X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.What is substance X?

A coenzyme

A substrate

An allosteric inhibitor

An intermediate

If an enzyme is added to a solution where its substrate and product are in equilibrium, what would occur?

Additional products would be formed.

Additional substrate would be formed.

The free energy of the system would change

Nothing; the reaction would stay at equilibrium.

Which one of the following is the mechanism of action of enzymes?

They act upon substrate molecules to release new substrate molecules.

They actually increase the amount of energy of activation.

Enzymes dramatically decrease the amount of energy of activation.

Enzymes break product molecules to release new product molecules

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?

By binding at the active site of the enzyme

By changing the shape of a reactant

By changing the free energy change of the reaction

By acting as a coenzyme for the reaction