carbohydrate metabolism saccharide metabolism GO:0005975 Metabolism of carbohydrates. Carbohydrates are essential structural component of living cells and source of energy. They include simple sugars with small molecules as well as macromolecular substances. Carbohydrates are any of a group of organic compounds based of the general formula Cx(H2O)y. Carbohydrates are classified according to the number of monosaccharide groups they contain. UPa:UPA00411 sugar metabolism pathway metabolic intermediate metabolism