SUMMARY
Polysaccharides (glycans) serve as stored fuel and as structural components of cell walls and extracellular matrix.■ The homopolysaccharides starch and glycogen are stored fuels in plant, animal, and bacterial cells. They consist of D-glucose with linkages, and all three contain some branches.■ The homopolysaccharides cellulose, chitin, and dextran serve structural roles. Cellulose, composed of (1n4)-linked D-glucose residues, lends strength and rigidity to plant cell walls. Chitin, a polymer of (1n4)-linked N-acetylglucosamine, strengthens the exoskeletons of arthropods. Dextran forms an
adhesive coat around certain bacteria.