carbohydrate metabolism carbohydrate biosynthesis The formation from simpler components 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:UPA00412 pathway sugar biosynthesis GO:0016051 saccharide biosynthesis