Carbohydrates are grouped according to the number of carbon atoms per molecule, such as the trioses (three-carbon unit), the pentoses (five-carbon unit), and the hexoses (six-carbon unit). Nutritionally, the most important carbohydrates are the hexoses. Three homopolysaccharides of glucose comprise the major dietary carbohydrates and the major carbohydrate store of liver and muscle. While glucose is the most important metabolic carbohydrate, glucose, galactose, fructose, and other monosaccharides are infrequent dietary carbohydrate constituents. Insignificant amounts of glucose are naturally consumed in diets. Hemicelluloses, pectins, gums, and mucilages are heteropolysaccharides: polysaccharides composed of the monosaccharides glucose, galactose, pentoses, uronic acid, and so on. These carbohydrates, present in plants, together with cellulose and lignin, constitute what is called dietary fiber. Glucose and similar monosaccharides from starch, cellulose, and most other components of dietary fiber possess the same caloric values following intestinal absorption, irrespective of the source of hydrolytic enzymes.