Glucose isomer models. Molecular models of the glucopyranose form of glucose. Glucose (C6H12O6) is a hexose sugar. Glucopyranose has a five carbon ring and an additional asymmetric carbon atom. Carbon atoms are black, hydrogen are white, and oxygen are red. The placement of the hydroxyl group (OH) determines whether the isomer is alpha or beta-glucose. Glucose is found in many plants and is a normal constituent of blood. It is widely used in the confectionary industry as a sweetener.