Answer is : (b) α - helix, β - pleated sheet
The two important types of secondary structures of proteins are α - helix and β - pleated sheet. β - sheets consist of β - strands connected laterally by atleast two or three backbone H - bonds, forming a generally twisted, pleated sheet. A β - strand is a stretch of polypeptide chain, 3 -10 amino acids long with backbone in an extended conformation.
In α - helix, the chain is spirally coiled, generally in a right - handed manner. This structure is formed through H - bonding in single amino acid chain only.
