Final answer:
The active site is the region within an enzyme where the substrate binds for the reaction. It is a small region within the enzyme and contains amino acid residues that participate in the catalytic action.
Step-by-step explanation:
The active site is the region within an enzyme where the substrate binds for the reaction.
Enzymes are usually proteins having primary, secondary, and tertiary structures. The active site is usually a small region (10% to 20%) within the enzyme. A few side chains of amino acid residues within the active site participate in the catalytic action.