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Consider the following statements about insulin
$I$. Human insulin is made-up of $51$ amino acids arranged in two polypeptide chains
$II$. The two polypeptide chains are interconnected by two disulphide bridges
$III$. In mammals including humans, insulin is synthesized as a pro-hormone, which contains an extra stretch called the Cpeptide
$IV$. $C-$peptide is not present in the mature insulin
Which of the statements given above are correct?
$I$, $II$ and $III$
$I$, $III$ and $IV$
$II$, $III$ and $IV$
$I$, $II$, $III$ and $IV$
Solution
Human insulin is made up of $51$ amino acids arranged in two polypeptide chains. A having $21$ amino acids and $B$ with $30$ amino acids. The two polypeptide chains are interconnected by two disulphide bridges or $S-S$ linkages. $S-S$ linkage also occurs in $A-$chain. The hormone develops from the storage product is called proinsulin. Proinsulin has three chains, $A , B$ and $C \cdot C$ chain with $33$ amino acids is removed prior to insulin formation
