Answer:
Substrate.
Step-by-step explanation:
Chemical reactions may be defined as the reactions in which the reactant is converted into the product. The new substance will always form at the end of the chemical reaction.
The enzymes are required for the biochemical reaction. The reactant is named as substrate in these reactions. The substrate combines with enzyme to form enzyme - substrate complex and its further converted into the product at the end of reaction.
Thus, the correct answer is option (e).