Metabolism are the chemical reactions that happen in the body and are required to maintain life. These reactions can be broken down into two categories, catabolism and anabolism.


Catabolism include reactions that break down larger molecules into smaller ones. Food is broken down into smaller, usable pieces.


Anabolism includes reactions that build larger molecules from smaller ones. Building proteins from amino acids is an example. Anabolic steroids increase anabolism, making the body build more muscle proteins.

Biosynthesis is anabolism.

Overview of metabolism: Anabolism and catabolism at Khan Academy.