What are the common types of secondary structure of proteins?

There are two common types of secondary structure of proteins:

(i) ∝-helix structure

(ii) β-pleated sheet structure

∝- Helix structure:

In this structure, the −NH group of an amino acid residue forms H-bond with the  group of the adjacent turn of the right-handed screw (∝-helix).

β-pleated sheet structure:

This structure is called so because it looks like the pleated folds of drapery. In this structure, all the peptide chains are stretched out to nearly the maximum extension and then laid side by side. These peptide chains are held together by intermolecular hydrogen bonds.