Question

what is a substrate?
the location on the enzyme where chemical reactions take place
the products of a chemical reaction that has been catalyzed by an enzyme
a reactant molecule that forms a temporary association with an enzyme before being converted to a product
the catalyst of a chemical reaction

Explanation:

A substrate is a reactant that binds to an enzyme's active - site, forms a temporary complex, and is then converted into a product. The location on the enzyme where reactions occur is the active - site. The products are what the substrate is converted into. The catalyst of a chemical reaction is the enzyme itself, not the substrate.

Answer:

A reactant molecule that forms a temporary association with an enzyme before being converted to a product