Definition of Polypeptide
A polypeptide is an organic molecule having a long, continuous and unbranched chain consisting of about 50 amino acid residues. The amino acids are the building blocks (monomers) of these polypeptides and they are linked with each other by the help of peptide bonds.
A peptide bond is formed when the amino group of one amino acid forms a bond with the carboxyl group of the second amino acid with the emission of a water molecule. The polypeptides which consist of more than 50 amino acid residues are termed as a protein.