Any of a group of carbohydrates comprising long chains of monosaccharide (simple sugar) molecules. Homopolysaccharides consist of only one type of monosaccharide; heteropolysaccharides contain two or more different types. Polysaccharides typically consist of several hundred to several thousand monosaccharides joined by glycosidic linkages. They may have molecular weights of up to several million and are often highly branched. Major storage polysaccharides include starch and glycogen, whereas structural polysaccharides include cellulose and chitin.