Enzymes as Catalysts 3.3

Q: What are enzymes?

A: Enzymes are biological catalysts that speed up the rate of reactions.

Q: How do enzymes speed up reactions?

A: They reduce the potential energy of the transition state, lowering the activation energy (Ea).

Q: What happens when activation energy is lowered?

A: Products are produced at a faster rate.

Q: Do enzymes change the composition of the products?

A: No, catalysts do not alter the physical composition of the products.

Q: What is activation energy?

A: The minimum amount of energy required to break the bonds in a chemical reaction.

Q: What two requirements must be met for a chemical reaction to occur?

• Molecules must be in the correct orientation.

• Molecules must collide with enough force.

Q: How does temperature affect molecular collisions?

A: Temperature can increase the collisions

between molecules

• It causes the molecules to move at a high

speed, forcing more collisions

• In turn, new bonds can form

Q: What happens when molecules move faster and collide more?

A: New bonds can form more easily.

Q: What are the negative effects of high temperature?

• It can cause enzyme denaturation.

• It can increase the rate of all chemical reactions, which may overwhelm the cell.

Q: How do enzymes affect activation energy?

A: Enzymes lower the activation energy of a reaction.

Q: What happens when activation energy is lowered by enzymes?

A: Reactants reach the transition state faster.

Q: Do enzymes change the reactants or products?

A: No, enzymes do not alter their composition.

Q: What happens to the free energy in enzyme-catalyzed reactions?

A: It remains unchanged.

Q: What are three main ways enzymes lower activation energy?

A) Promotes Collisions – Enzymes bind to molecules to bring them closer together.
B) Exposure to Charged Environments – Active site contains ionic groups that attract or repel substrates to favor catalysis.
C) Changes Shape of Substrate – Enzyme strains bonds in the substrate, allowing reactions to occur more easily.