This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Physiology
True statement regarding insulin 
Select and explain. 
A. Circulated in blood by binding with RBC, B. Made of 2 chains with 3 disulphide bonds, C. Synthesized by alpha cells of islet of langerhans, D. Elimination half life is 60 min. after subcutaneous injection
B: Made of 2 chains with 3 disulphide bonds
Answer: B: Made of 2 chains with 3 disulphide bonds 
Explanation: Insulin is the major fuel-regulating hormone of the body, a double-chain protein formed from proinsulin in the beta cells of the islets of Langerhans in the pancreas. Insulin promotes the storage of glucose and the uptake of amino acids, increases protein and lipid synthesis, and inhibits lipolysis and gluconeogenesis. Secretion of insulin is a response of the beta cells to a stimulus; the primary stimulus is glucose, and others are amino acids and hormones such as secretin, pancreozymin, and gastrin. These chemicals play an impoant role in maintaining normal blood glucose levels by triggering insulin release after a meal. Ref: Ganong&;s review of medical physiology;24th edition; page no-432