metabolism

the sum of all the physical and chemical changes within CELLS and tissues that maintain life and growth. The breakdown processes that occur are known as catabolic ( CATABOLISM ), and those that build materials up are called anabolic (anabolism). The term may also be applied to describe one particular set of changes, e.g. PROTEIN metabolism. Basal metabolism is the minimum amount of energy required to maintain the body's vital processes, e.g. heartbeat and respiration, and is usually assessed by means of various measurements taken while a person is at rest.