alphaDglucopyranosyl12betaDfructofuranoside

Alpha-D-glucopyranose, often written α-D-glucopyranose or α-D-glucose, is the alpha anomer of the six-carbon aldose D-glucose in its cyclic pyranose form. In solution glucose can cyclize to a six-membered ring (pyranose) and exist as two anomers, alpha and beta, which interconvert through mutarotation. The designation alpha refers to the orientation of the hydroxyl group on the anomeric carbon (C1); in the standard representation for D-glucose, the C1 hydroxyl is on the opposite side of the ring from the CH2OH substituent at C5.

Alpha-D-glucopyranose is a stereoisomer of D-glucose and has the same chemical formula as its beta counterpart, but a different spatial arrangement at C1. In aqueous solution, alpha and beta forms are in equilibrium, along with the open-chain form. The alpha and beta forms can interconvert, a process known as mutarotation, which depends on temperature and solvent conditions.

Biologically, glucose serves as a primary energy source in many organisms. D-glucose is the monomer unit for several polysaccharides: starch and glycogen are composed predominantly of α-D-glucose residues linked by α-1,4 glycosidic bonds (with α-1,6 branches in glycogen), while cellulose is built from β-D-glucose units. The properties and reactivity of α-D-glucose underpin fundamental pathways such as glycolysis and other carbohydrate metabolism processes. The molecule is colorless, highly soluble in water, and widely distributed in nature, occurring in fruits, honey, and as a product of photosynthesis.