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.
The sugars are the hexose sugars, characterized by the presence of six carbon atoms in the molecule and by an empirical formula of C6H12O6.
The disaccharide sugars, maltose, lactose, and sucrose, have the empirical formula C12H22O11.
