Question

In α-helix secondary structure, hydrogen bonds lie between imide group of one amino acid and carbonyl group of
A) Second Amino acid
B) Third Amino acid
C) Fourth Amino acid
D) Fifth Amino acid

Answer 1

Hint: α-helix secondary structure is the most commonly found structure of protein. The amino acids are arranged in a right handed helical structure.

Complete Answer:
The proteins are chains of amino acids. If the arrangement of amino acids in the chain is linear (peptide bond between amino acids) then the structure is called primary protein. If it is further coiled it is called secondary chin. In the secondary chain, other than peptide bonds between the amino acid, hydrogen bonds are also present to give a coiled structure. There are two types of secondary structure-
1) α-helix- It is a right handed helical structure in which 3.6 amino acids are present in a single turn. There occurs a hydrogen bond between the N-H group of amino acid C = O group of the fourth amino acid.
2) Beta pleated sheet- It is a twisted or pleated structure of proteins in which one layer of amino acid forms bonds between the other layers.

Thus the correct answer is (C). The hydrogen bond is present in between the N-H group and C=O group of Fourth amino acid.

Note: The backbone hydrogen bond of α-helix is weaker than that of beta sheets. Thus can be broken easily by water molecules. The α-helix are more stable to mutations.