sugar /sho͝og″ər/ [Gk, sakcharon] , any of several water-soluble simple carbohydrates. The principal categories of sugars are monosaccharides, disaccharides, and polysaccharides. A monosaccharide is a single sugar, such as glucose, fructose, or galactose. A disaccharide is a double sugar, such as sucrose (table sugar) or lactose. A polysaccharide is a sugar made up of repeating units of glucose, such as cellulose, starch, and glycogen. Sugars play an important role in biology by either forming conjugates with other biomolecules (e.g., glycoproteins) or by mediating cell surface recognition events (e.g., bacterial or viral binding to cells). See also carbohydrate, fructose, galactose, glucose, saccharide, sucrose.
