Sugar
. Sugar, term applied loosely to any of a number of chemical compounds in the carbohydrate group that are readily soluble in water; are colorless, odorless, and usually crystallizable; and are more or less sweet in taste. In general, all monosaccharides, disaccharides, and trisaccharides (see Carbohydrate ) are termed sugars, as distinct from polysaccharides such as starch , cellulose , and glycogen. Sugars, which are widely distributed in nature, are manufactured by plants during the process of photosynthesis and are found in many animal tissues (see Sugar Metabolism ). Ribose, a monosaccharide sugar containing five carbon atoms in its molecule, is a constituent of the nuclei of all animal cells; five-carbon sugars are known as pentoses. Trioses (three-carbon sugars), tetroses (four-carbon sugars), heptoses (seven-carbon sugars), octoses (eight-carbon sugars), and nonoses (nine-carbon sugars) are also found in nature, but the most widespread of the sugars are the hexose sugars, chara