What are the functions of insulin?

1. Promotes glucose transport into all cells of the body except brain. Rapid transport of glucose into the cells decreases the blood glucose concentration. On the other hand, lack of insulin causes glucose to be accumulated in the blood.

2. Promotes glycogen storage in the liver and muscle. The glycogen concentration in liver cells sometimes increases to as high as 5 to 6 percent and in muscle cells to over 1 percent. After liver and muscle stores of glycogen have been filled, the rest of the glucose is stored in the fat tissue. Insulin helps in the transport of glucose in these cells.

Besides these functions, insulin also:

1. Helps in the transport of most of the amino acids through the cell membrane, and

2. Increases the formation of protein and RNA in cells.