A tetrapeptide has -COOH group on alanine. This produces glycine (Gly), valine (Val), phenyl alanine (Phe) and alanine (Ala), on complete hydrolysis. For this tetrapeptide, the number of possible sequences (primary structures) with -NH2 group attached to a chiral center is

Question

A tetrapeptide has -COOH group on alanine. This produces glycine (Gly), valine (Val), phenyl alanine (Phe) and alanine (Ala), on complete hydrolysis. For this tetrapeptide, the number of possible sequences (primary structures) with -NH2 group attached to a chiral center is (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

No. of possible sequences (primary structures) with

- N H_{2}

group attached to a chiral center is 4.
Since

-COOH

group is attached to alanine, one terminal of the tetrapeptide contains alanine. Thus, its position is fixed.
Glycine is achiral whereas valine and phenylalanine are chiral. Thus,

-NH_{2}

group is attached to either valine or phenylalanine.
Thus following are the four possible combinations of the tetrapeptide.

H_{2} ​ N - Va l - Gl y - P h e - A l a - COO H

H_{2} ​ N - Va l - P h e - Gl y - A l a - COO H

H_{2} ​ N - P h e - Gl y - Va l - A l a - COO H

H_{2} ​ N - P h e - Va l - Gl y - A l a - COO H

Q. A tetrapeptide has −COOH group on alanine. This produces glycine (Gly), valine (Val), phenyl alanine (Phe) and alanine (Ala), on complete hydrolysis. For this tetrapeptide, the number of possible sequences (primary structures) with −NH2​ group attached to a chiral center is

Q. A tetrapeptide has $- COO H$ group on alanine. This produces glycine (Gly), valine (Val), phenyl alanine (Phe) and alanine (Ala), on complete hydrolysis. For this tetrapeptide, the number of possible sequences (primary structures) with $- N H_{2}$ group attached to a chiral center is