What is a polypeptide

Peptides are among the various amino acids formed by dehydration polymerization of organic compounds with peptide bonds. Different from polymer, monomer (monomer) is a kind of amino acid residue which is the basic construction of peptide chain. Peptide is not a polymer. Compared with the protein, the chain structure of the covalent bond is the same as that of the former. Therefore, peptides are not proteins. However, there are a lot of similar physical and chemical properties between peptides and proteins, such as hydrophilicity, polarity, two class structure, enzymatic hydrolysis, metal complexation and so on. It is difficult to distinguish peptides from proteins on an exact value from the molecular weight. So far, people are accustomed to the length of the peptide chain as follows:

Less than 10 residues are oligopeptides (oligopeptide) or small peptide molecules. 10~80 (or 100) residues are polypeptides (polypeptide) or peptides. More than 80 (or 100) residues are proteins, and it is argued that only molecules with more than 150 or more residues are the real proteins.