Question

Which one is imino acid?
A. Pepsin
B. Proline
C. Cysteine
D. Renin

Answer 1

Hint: Amino acids containing secondary amine groups are known as imino acids. It consists of $NH$ group and in case of amino acid $N{H_2}$ group. Imino acid found in protein structure.

Complete answer:
Amino acid is an organic compound with one amino and one carboxyl group attached to it but in case of imino acid there is a secondary amine group and a carboxyl group. Proline has a second amino group whereas cysteine has only a primary group and there is no secondary group.

> Option A- Pepsin: It is an enzyme secreted by chief cells of the stomach. They are secreted in the form of pepsinogen that is their inactive form and when they are exposed to HCL of stomach they convert into pepsin. It helps in the digestion of the proteins.

> Option B- Proline: It has a secondary amino group attached to it and thus it is called as imino acid. It is important for the formation of healthy cartilage and collagen in our body and it also affects flexibility of both muscles and joints.

> Option C- Cysteine: It has an attached primary group of amino acids. It has an important function in the human body of producing antioxidants, growth of hairs, reducing skin ageing effects, source of energy etc.

> Option D- Rennin: It is secreted by kidneys in the circulation when there is renal hypotension and hypernatremia, it is a protease enzyme.

Hence, the correct answer is option (B).

Note: Proline is used for various processes, it is required for proper functioning of joints and tendons, it also helps in maintaining strength of heart muscles. It is important for maintaining reparative function of muscles as well as youthful skin is maintained by it. It plays its role in the immune system also.