Amino acids can be classified as α-, β-, - , δ- and so on depending upon the relative position of amino group with respect to carboxyl group. Which type of amino acids form polypetide chain in proteins?
α-amino acids, alpha-amino acids, where the amino acid is linked to the α-carbon in the molecule are the type of amino acids which form a polypeptide chain. α-amino acids are obtained on hydrolysis of proteins. β-, - , δ- are non-proteinogenic amino acids, and are classified according to the carbon group to which an amino group is attached to. They are called non-proteinogenic as they do not form peptide chains, as the different positions of the –NH2 and the –COOH group do not allow the formation of a fixed polypeptide structure.