Insulin is a hormone produced by the beta-cells of the pancreas. It is a protein with a molecular weight of approximately 5700 kDa. It is formed from proinsulin after cleavage into insulin and C-peptide (Fig 1).
The normal insulin secretion is 0.5-0.7 units/kg per day.

Fig 1: Insulin has two chains A and B and during its production. A third chain of peptides called C Peptide links these. C peptide is removed before Insulin is secreted into the blood.

Physiological Functions of Insulin

Stimulates entry of glucose into cells for utilization as energy source.

Stimulates entry of amino acids into cells, enhancing protein synthesis

Enhances fat storage and prevents mobilization of fat for energy (lipolysis)

Promotes storage of glucose as glycogen in muscle and liver cells (glycogenesis)

Inhibits formation of glucose from non carbohydrates (gluconeogenesis)

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