What are peptides?

Peptides consist of amino acids, which are structural and functional fragments of proteins, and make proteins have tens of millions of physiological functions. Peptides themselves also have strong biological activities. Peptides derived from dehydration and condensation of two or three amino acids are called dipeptides and tripeptides, which are analogous to tetrapeptides and pentapeptides. Generally speaking, the number of amino acids in the peptide chain is less than 10 called oligopeptides, and up to 10-50 are called polypeptides, and more than 50 are called proteins. At present, all of them can be synthesized artificially. The degree of difficulty in synthesis and the size of physiological activity are protein, polypeptide and oligopeptide in turn. According to molecular weight, oligopeptides and peptides belong to small molecules and proteins are macromolecular compounds. Insulin is known to consist of 51 amino acids and is the smallest protein synthesized.