Enzymes are protein molecules which serve as catalysts for chemical reactions. A catalyst is a substance which will decrease the activation energy for a reaction. ... Enzymes will make reactions occur much more easily, quickly and more efficiently than they ever would without the enzyme.
High energy produced during the metabolism of reactant to product. Due to the large free energy of activation, the speeds of uncatalyzed biochemical reactions are often exceedingly slow. Enzymes lower this energy of activation so that more molecules have adequate energy to carry into the transition state to speed up the rate of reaction.
