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. There are 20 naturally-occurring amino acids and, like letters into words, they can be combined into an immense variety of different molecules. When a molecule consists of 2-50 amino acids it is called a peptide, whereas a larger chain of > 50 amino acids generally is referred to as a protein. Peptides are in every cell and tissue in the body.