In a chemical reaction, enzymes act as a:

Correct answer: Catalyst. Enzymes are biological catalysts that speed up reactions without being used up.

Background: Most enzymes are proteins.

• Inhibitor: An inhibitor slows a reaction.
• Reactant: A reactant is used up in a reaction.
• Product: A product is formed by a reaction.

Did you know? Enzymes work best at a certain temperature and pH.

Memory trick: Enzyme = biological catalyst.