In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate(s). The substrate binds with the enzyme's active site, and an enzyme-substrate-complex is formed. The substrate is broken down into a product and is released from the active site. The active site is now free to accept another substrate molecule.

A general equation is as follows:

E + S <--> ES --> EP <--> E + P

where E = enzyme, S = substrate(s), P = product(s)

Note that only the middle step is irreversible.

Biochemistry

Substrato | Substrat (chemia) | Substrat | 底物