This is a hormone — a chemical produced in one area of the body and released into the blood. Insulin is produced in the pancreas. It travels through the blood stream to tissues such as the liver, fat cells and muscles. Insulin fits itself to receptors on these tissues. Then the cell responds with a flurry of activity. It sends molecules to the membrane of the cell to bring in glucose— a sugar the cell needs to function.
Sometimes a person’s body can’t produce enough insulin or stops making it altogether. In other people, their body stops responding to the insulin they do have. When this happens, these people develop a potentially deadly disease called diabetes. They may have to take injections of insulin every day to remain healthy.