Digestive enzymes pay an important role in digestion as they regulate the chemical reactions in the breakdown of food. Most digestive enzymes are hydrolases and produce their catalytic action by the process of hydrolysis, in which a molecule of water is chemically added to the food molecule, which then separates into two or more smaller molecules.
In hydrolysis, cleavage may involve several stages before the final molecules are obtained. Like carbohydrate metabolism, the metabolism of lipids is also influenced by hormones. Lack of insulin affects fat metabolism, for lipogenesis is impeded both in in the liver and the adipose tissue.