What does insulin do?

Diabetes is a metabolism disorder where the pancreas fails to produce insulin, which is like the key that controls the movement and storage of fuel (glucose).
The body uses two types of fuel - glucose and fats. Carbohydrate are the most readily available source of glucose and can easily be converted into fuel for immediate use. Some glucose will be stored in the liver and muscles as glycogen to be used later and during exercise. Carbohydrates not needed for immediate energy or for replacement of glycogen will be converted to fat. Insulin is required for each of these processes of storage and conversion of carbohydrates.
Protein, which is made up of amino acids, can be another source of glucose, if the body does not receive enough carbohydrates to use as a fuel source. When insulin is present the liver can change some of the amino acids into glucose. Insulin also allows amino acids to be used for building and repairing muscle and body tissues (in other words for healing our injuries).Fat fuel in the form of triglycerides is absorbed from the intestines. Insulin allows triglycerides to go directly into fat cells where it is stored and used for future energy needs.
Insulin, therefore, is important not only for the conversion of glucose, sugar and carbohydrates into fuel (energy), but in the use of proteins and fat as well.