Insulin is a primary hormone used by the human body to control blood sugar levels and control the glycogen metabolism. Insulin hormone is a 51-residue protein made in the pancreas by the Beta cells of the pancreatic Islet and is released when glucose concentrations exceed normal levels. The hormone affects metabolism when it binds to a receptor protein on the plasma membrane of a cell. It increases the rate of glucose uptake into the muscle and adipose tissues through the GLUT4 glucose transporter. This process is a facilitated diffusion so no ATP is used. When insulin binds to the receptors on the cell surface, vesicles containing the GLUT4 transporters come to the plasma member and fuse together by the process of exocytosis.

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When this vesicle fuses, it increases the capacity of the cells to transport glucose as more transporters are present on the plasma membrane. Insulin also has other wide reaching effects in the body. It leads to the acceleration of Glucose utilization because of the increased amounts of glucose in the plasma membrane and enhanced ATP production since it activates key enzymes involved in the initial steps of glycolysis. Insulin in also involved in stimulating Glycogen formation in the skeletal muscles and liver cells and stimulates the triglyceride formation in Adipose tissue. Once the glucose enters the cell, it is phosphorylated into Glucose-6-Phosphate in order to preserve the concentration gradient so glucose can continue to enter the cell (instead of the other way around).

When insulin hormone is not being produced or there is a deficiency, it leads to the disease state known as Diabetes which can have far reaching secondary complications such as kidney failure, blindness, damages blood vessels and much more. Thus Insulin is an important pancreatic endocrine hormone necessary in the human body for blood sugar level regulation and energy production of the body as glucose becomes phosporylated and enzyme activated for glycolysis.

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Horton, Robert, Moran Laurence, Perry Marc, Rawn David and Scrimgeour Gray. Principles of Biochemistry. Upper Saddle River, New Jersey: Pearson Education Inc, 2006.