Catabolism - Definition

Anabolism is the aspect of metabolism that contributes to growth. One way of categorizing metabolic processes, whether at the cellular, organ, or organism level is as anabolic or catabolic.

Anabolic processes tend toward "building up" organs and tissues. These processes produce growth and differentiation of cells and increase in body size. Examples of anabolic processes include growth and mineralization of bone and increase of muscle mass.

Catabolism: Catabolic processes involve "breaking down" organs and tissues. These processes involve "dismantling" of structural proteins for recycling for other purposes. Catabolic processes occur during starvation, stress, and illness. Examples of catabolic processes include breakdown of muscle protein in order to use amino acids as substrates for gluconeogenesis (metaphorically burning furniture in your house to burn as fuel because you are out of firewood), and breakdown of fat in adipose to fatty acids for fuel.

Because it is counterproductive to have anabolic and catabolic processes occurring in cells simultaneously, there are many signals that switch on anabolic processes while switching off catabolic processes and vice versa. Most of the known signals are hormones of various types. Endocrinologists have traditionally classified many of the hormones as anabolic or catabolic.

• Classic anabolic hormones include
  • Growth hormone
  • IGF1 and other insulin-like growth factors
  • Insulin
  • Testosterone
  • Estrogen
• Classic catabolic hormones include
  • Cortisol
  • Glucagon
  • Adrenalin and other catecholamines
  • Cytokines

Like most broad generalizations about complex systems, this dichotomy is a heuristic oversimplification.

See also

Anabolic steroids