This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition & Digestion, Subject name: Biochemistry
Metal required for polymerization of insulin is: 
Select and explain. 
A. Copper, B. Chromium, C. Cobalt, D. Zinc
D: Zinc
Answer: D: Zinc 
Explanation: Ans. D. ZincInsulin is produced by b-cells of pancreas and consists of 51 amino acids. Chain A has 21 amino acids and chain B has 30 amino acids. Both are held together by two inter chain disulfide bridges. In the b-cells, insulin (also called proinsulin) combines with zinc to form complexes. It is stored in this form in the granules of the cytosol.