alpha-D-glucose hydrate is a monosaccharide and the most common form of glucose. It is a monosaccharide, which means it cannot be broken down into simpler sugars. alpha-D-glucose plays a vital role in energy metabolism and is the primary source of energy for many cells in the body. It is also a building block of larger carbohydrates such as starch and glycogen. The “α” prefix refers to the orientation of the hydroxyl group attached to the first carbon atom. Alpha-D-glucose exists in solution as a hydrate, which means it is bound to water molecules.