A polypeptide with more than hundred
amino acid residues, having molecular mass higher than 10,000u is called
a protein However, the distinction between a polypeptide and a protein is
not very sharp Polypeptides with fewer amino acids are likely to be called
proteins if they ordinarily have a well defined conformation of a protein such
as insulin which contains 51 amino acids Proteins can be classified into two types on the basis of their
molecular shape