Q. Describe the effects of insulin on carbohydrate metabolism?
Insulin promotes muscle glucose uptake and metabolism. In presence of insulin muscle cells take up glucose and use it as a source of energy. Insulin also promotes storage of insulin in the form of glycogen in the muscle cells. Later this glycogen can be broken down to glucose and used as a source of energy. But insulin prevents break down of glycogen to glucose in muscle cells. Only when insulin level is low, glycogen can break down to glucose.
Insulin also promotes uptake, storage and use of glucose in liver. After a meal good amount of glucose is absorbed from gastrointestinal tract and come into circulation. This absorbed glucose is taken up by liver cells and converted to glycogen. The liver stores good amount of glycogen. Insulin prevents break down of glycogen in liver. In between meals when both glucose and insulin levels of blood are low, liver glycogen is broken down to glucose and used as fuel.