betaDglucose

Beta-D-glucose is one of the two anomers of D-glucose, a hexose sugar that is a fundamental building block in biology. In its open-chain form it is an aldohexose with the formula C6H12O6 and an aldehyde group at C1. In aqueous solution glucose mainly exists as cyclic hemiacetals, occurring as beta-D-glucopyranose or alpha-D-glucopyranose depending on the configuration at the anomeric carbon (C1) after cyclization.

Beta-D-glucose is characterized by a hydroxyl group at C1 that is oriented equatorially in the cyclic form; in the Haworth projection the anomeric OH is drawn above the ring. The alpha form has the C1 hydroxyl on the opposite face. Glucose mutarotates between its alpha and beta anomers in solution, reaching an equilibrium at room temperature of roughly 36% alpha and 64% beta.

Functionally, beta-D-glucose is a precursor for cellulose, in which units are linked by β-1,4 glycosidic bonds to form a linear, rigid polymer. By contrast, starch and glycogen are polymers of alpha-D-glucose linked by α-1,4 and α-1,6 bonds. In its free form, beta-D-glucose can open to reveal a reactive aldehyde, so it is a reducing sugar.

In chemistry and biology, beta-D-glucose designates the beta anomer of the D-configuration; it is the D-enantiomer in common usage. Both alpha- and beta-D-glucose share the same molecular formula (C6H12O6) but differ at the anomeric carbon. The beta designation is especially used when describing monomers of cellulose and other beta-linked polysaccharides.