sugar

sugar compound of carbon, hydrogen, and oxygen belonging to a class of substances called carbohydrates . Sugars fall into three groups: the monosaccharides, disaccharides, and trisaccharides. The monosaccharides are the simple sugars; they include fructose and glucose . The disaccharides are formed by the union of two monosaccharides with the loss of one molecule of water. Disaccharides include lactose , maltose , and sucrose . Less well known are the trisaccharides; raffinose is a trisaccharide present in cottonseed and in sugar beets. Sugars belong to two families denoted by the letter d - or l - written before the name of a sugar. The families are related to glyceraldehyde CH ₂ OHCHOHCHO, which can exist in two three-dimensional forms that are mirror images of each other. The isomer of glyceraldehyde that rotates plane polarized light clockwise is labeled d -glyceraldehyde; all natural sugars can be derived from this substance and thus belong the the d family. Although l -sugars can be prepared in the laboratory, they cannot be utilized by animals.

sugar (shuug-er) n. any carbohydrate that dissolves in water, is usually crystalline, and has a sweet taste. Sugars are classified chemically as monosaccharides or disaccharides. Table sugar is virtually 100% pure sucrose. See also fructose, glucose, lactose.

sugar Sweet-tasting, soluble, crystalline monosaccharide or disaccharide carbohydrate. The common sugar in food and beverages is sucrose. This is also the main sugar transported in plant tissues. The main sugar transported around the bodies of animals to provide energy is glucose. See also saccharide