# The secondary structure of protein refers to

$\begin {array} {1 1} (A)\;\text{sequence of$ \alpha$amino acids }\\ (B)\;\text{fixed configuration of the polypeptide backbone} \\ (C)\;\text{$ \alpha$helical backbone}\\ (D)\;\text{hydrophobic instructions} \end {array}$

The secondary structure of proteins refers to fixed configuration of polypeptide chain
Ans : (B)
The next level of protein structure, secondary structure, refers to local folded structures that form within a polypeptide due to interactions between atoms of the backbone. (The backbone just refers to the polypeptide chain apart from the R groups – so all we mean here is that secondary structure does not involve R group atoms.) The most common types of secondary structures are the α helix and the β pleated sheet. Both structures are held in shape by hydrogen bonds, which form between the carbonyl O of one amino acid and the amino H of another.
edited Feb 19