Question -
Answer -
There are two common types of secondary structure ofproteins:
(i) ∝-helixstructure
(ii) β-pleatedsheet structure
∝– Helix structure:
In this structure, the −NH group of an amino acidresidue forms H-bond with the 
groupof the adjacent turn of the right-handed screw (∝-helix).
β-pleated sheet structure:
This structure is called so because it looks like thepleated folds of drapery. In this structure, all the peptide chains arestretched out to nearly the maximum extension and then laid side by side. Thesepeptide chains are held together by intermolecular hydrogen bonds.