Metabolism (from μεταβολισμος ("metabolismos")) is the biochemical modification of chemical compounds in living organisms and cells. This includes the biosynthesis of complex organic molecules (anabolism) and their breakdown (catabolism). Metabolism usually consists of sequences of enzymatic steps, also called metabolic pathways. The total metabolism are all biochemical processes of an organism. The cell metabolism includes all chemical processes in a cell.The Dynamic Energy Budget theory aims to quantify the metabolic organisation of individual organisms; many species are unicellular.

The term is derived from the Greek word for "change", or "overthrow" (Etymonline)).

Metabolic pathways