a-Helix is one of the most common ways in which
a polypeptide chain forms all possible hydrogen bonds
by twisting into a right handed screw (helix) with the
–NH group of each amino acid residue hydrogen bonded to the
C   O of an adjacent turn of the helix as shown in Fig 10 1 In b-pleated sheet structure all peptide chains are
stretched out to nearly maximum extension and then
laid side by side which are held together by
intermolecular hydrogen bonds