Define Functions of Carbohydrate - Source of energy?

Glucose is a major source of energy for all the body cells. One gram of carbohydrate provides 4 Kcal. RBCs are particularly dependent on glucose. It is also indispensable for the maintenance of functional integrity of the nerve tissue and under normal circumstances; it is the sole source of energy for the brain. Similarly, glucose is important for heart muscles. Although fatty acids are the preferred regular fuel of heart muscle, glycogen in cardiac muscle is an important emergency source of contractile energy. In a damaged heart, poor glycogen stores or low carbohydrate intake may cause cardiac symptoms of angina.