Physiology of Finfish and Shellfish (2+1)

4.3.2.2 Phases of metabolism

Total metabolism of any cell can be broadly divided into 2 phases – catabolism and anabolism.

Catabolism refers to all the degradative reactions involving degradation or breakdown of various complex molecules to smaller and simple molecules. The chemical energy of metabolites is conserved in the form of ATP OR Catabolism is the process that results in the release of energy through the breakdown of nutrients, stored materials and cellular substances.

Anabolism refers to all synthetic reactions involving synthesis of various molecules from smaller and simple precursor molecules. This process requires the input of chemical energy in the form of ATP. Anabolism refers to the chemical process, through which digested and absorbed products are used effectively to build or repair bodily tissues, or to restore vital substances broken down through metabolism.

(The anabolic process uses monomers to build polymers. A polymer is a large complex molecule made of many small molecules that are similar to each other. Those small molecules are called monomers. For example: Amino acids, which are simple molecules (monomers) through a series of anabolic chemical reactions, build proteins, which are large and complex molecules (polymers).

In living systems both catabolism and anabolism occur concurrently and simultaneously. The energy released during catabolism is required for anabolic reactions and for many other cellular activities like muscular contraction, active transport, osmotic works, etc. Catabolic reactions are oxidative, whereas anabolic reactions are reductive in nature.

The pathway of reactions that is accessible to both catabolism and anabolism is called amphibolic pathway which can be used catabolically