1)how is mature insulin different from pro insulin secreted by pancreas in humans?

Mature insulin consist of 2 short polypeptide chains- chain A and chain B, that are linked together by disulphide bridge. In mammals, including humans ,
Insulin is synthesised as apro hormone, which contains an extra stretch calledC peptide.
(this C peptide is not present in mature insulin and is removed during maturation into insulin)