Insulin (bovine) has 51 amino acids in A and B polypeptides. The polypeptide A possesses amino acids
(a) 31
(b) 21
(c) 20
(d) 30

Options

A. 31
B. 21
C. 20
D. 30

Answer

To solve the question regarding the number of amino acids in polypeptide A of bovine insulin, we can follow these steps:

### Step 1: Understand the Structure of Insulin
Insulin is a hormone composed of two polypeptide chains, known as polypeptide A and polypeptide B. Together, these chains contain a total of 51 amino acids.

### Step 2: Determine the Composition of the Chains
From the information provided, we know that:
- The total number of amino acids in both polypeptides is 51.
- We need to find out how many amino acids are specifically in polypeptide A.

### Step 3: Analyze the Options
The options given for the number of amino acids in polypeptide A are:
(a) 31
(b) 21
(c) 20
(d) 30

### Step 4: Recall Known Information
It is known that:
- Polypeptide A contains 21 amino acids.
- Polypeptide B contains the remaining amino acids, which would be 51 - 21 = 30 amino acids.

### Step 5: Select the Correct Option
Based on the known composition of the polypeptides:
- Polypeptide A has 21 amino acids.

Thus, the correct answer is **(b) 21**.