Step-by-step explanation:
Enzymes are defined as protein molecules which are like catalysts, that is, like catalysts enzymes also help in increasing the rate of a reaction without itself getting consumed in the reaction.
The enzyme acts as a lock whereas the substrate acts as a key. When active site of enzyme binds to the active site of substrate then it results in the formation of a chemical reaction that speeds up because of correct binding of both enzyme and substrate together.
Thus, we can conclude that in a biological reaction involving the enzyme binds to active site of substrate.