Final answer:
Enzymes are proteins that catalyze chemical reactions by lowering activation energy. They have an active site where substrates bind and undergo a chemical transformation. Enzymes work by bringing substrates together, altering bond structures, providing optimal conditions, or participating directly in the reaction.
Step-by-step explanation:
Enzymes are macromolecules, usually proteins, that function as catalysts to speed up chemical reactions in living organisms. They have a specific region called the active site where substrates, the reactants in an enzymatic reaction, bind and undergo a chemical transformation. Enzymes work by lowering the activation energy of a reaction, making it easier for the reaction to occur. This is achieved through various mechanisms such as bringing substrates together in an optimal orientation, compromising the bond structures of substrates, providing optimal environmental conditions, or directly participating in the chemical reaction.