Metabolism encompasses all the chemical processes that occur within a living organism in order to maintain life. It includes two main categories:

* Anabolism: The building up of complex molecules from simpler ones, requiring energy. Examples include protein synthesis and the formation of glycogen from glucose.

* Catabolism: The breaking down of complex molecules into simpler ones, releasing energy. Examples include the breakdown of carbohydrates for energy or the digestion of food.

Metabolism is essential for all living organisms, allowing them to grow, reproduce, and maintain their internal environment. It is a highly regulated process, with different enzymes controlling each specific reaction.