Final answer:
Enzymes speed up reactions by lowering activation energy, which they achieve by providing an optimal orientation of substrates, compromising substrate bond structures, and sometimes temporarily forming covalent bonds with substrates. They are not changed or consumed by the reaction.
Step-by-step explanation:
Enzymes accelerate chemical reactions by lowering the activation energy required for the reaction to proceed, rather than changing the overall energy of the reactants or the products. They accomplish this by providing a unique chemical environment in their active sites where substrates are brought to an optimal orientation. This orientation supports the formation of unstable intermediates, or transition states, making the formation of products more favourable without altering the reaction's thermodynamics. Enzymes facilitate the transformation of substrates into products by compromising the bond structures of substrates, making bonds easier to break, and sometimes by forming transient covalent bonds with the substrates, all of which reduce the activation energy. It is important to note that although enzymes participate in reactions, they are not consumed in the process and can continue to catalyze subsequent reactions. By doing so, enzymes provide an alternate route for the reaction with lower activation energy, which increases the reaction rate.