Catalysts are substances, which speed up chemical reactions. Enzymes also have this ability. They speed up chemical reactions by reducing the activation energy, as well as chemical catalysts. However, enzymes are different from them, because they are large organic molecules unlike simple chemical catalysts, and enzymes are capable of regulation. Thus, to distinguish between enzymes and chemical catalysts, as well as to make emphasis on their biological origin, enzymes are called biocatalysts.