Question

How many amino acids are present in insulin?
A. $25$
B. $51$
C. $20$
D. $22$
E. $52$

Answer 1

Amino acids are the organic compounds that comprises two functional groups namely; amino and carboxyl functional groups. The amino group is denoted by $- N{H_2}$ and the functional group $- COOH$ stands for the carboxyl group.

Complete step by step solution
There are $51$ amino acids present in the insulin. Amino acids are colourless crystalline solids with high melting point. Also amino acids are soluble in water and act like salt rather than simple carboxylic acid or amine. This is because they contain both acidic i.e. carboxyl groups as well as basic i.e. amino groups. In aqueous solution, the amino acids give rise to zwitter ion which is a dipolar ion. In this form the amino acids show amphoteric behaviour and react with both acid and base.

We know that Insulin is a hormone responsible for maintaining the blood sugar level. It is made up of $51$ amino acids. Two peptide chains; A chain and B chain together make the insulin. Both the chains; chain A and chain B are linked together with the help of two disulphide bonds. Chain A contains $21$ amino acids and the B chain contains $30$ amino acids. In this way there are $51$amino acids present in the insulin. Insulin in its active form in the body is a monomer while in the potential form it is a hexamer.

**Hence, option (B) $51$ , is the correct option.

Note: **
Thus, insulin is a protein which is made up of two chains namely chain A and chain B. Chain A comprises $21$ amino acids whereas chain B contains $30$ amino acids. In total there are $51$ amino acids in insulin. Insulin is a hormone responsible for the regulation of sugar level in the blood.