The Gibbs free energy of the product is the same as it would be without the enzyme. Thus, the enzyme does not affect the free energy of the reaction.
The chemical or metabolic conversion refers to a reaction. The chemical which is converted into a product is called a 'substrate'. Hence enzymes, i.e., proteins with three dimensional structures including an 'active site', convert a substrate (S) into a product (P).
Enzymes lower activation energy of reactions and greatly enhance the rate of the reactions.
Enzymes are highly specific both in the reactions that they catalyze and in their choice of reactants, which are called substrates.
(E) An enzyme like any protein has a primary structure, i.e., amino acid sequence of the protein. An enzyme like any protein has the secondary and the tertiary structure.
(F) The energy input needed to start a chemical reaction is called activation energy

──────────────────────────────────────────────────────────────────────────────────────────