Question

what is a substrate?
a molecule that acts as a catalyst
a place on the enzyme where the reaction occurs
a place on the product where the enzyme fits
a reactant that is catalyzed by an enzyme

Explanation:

• A molecule that acts as a catalyst is an enzyme, not a substrate.
• A place on the enzyme where the reaction occurs is the active site.
• A place on the product where the enzyme fits is not a correct description.
• A substrate is defined as a reactant that is catalyzed by an enzyme.

Answer:

a reactant that is catalyzed by an enzyme