Peptides are chemical compounds consisting of two or more amino acids linked in a chain, the carboxyl group of each acid being joined to the amino group of the next by a bond of the type -OC-NH-.

Peptides are defined as molecules that consist of between 2 and 50 amino acids, whereas proteins are made up of 50 or more amino acids.

Peptides are naturally occurring biological molecules. Peptides are found in all living organisms and play a key role in all manner of biological activity. Like proteins, peptides are formed (synthesized) naturally from transcription of a sequence of the genetic code (DNA).