Topic overview

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Polysaccharides may be linear or branched and are classified as homopolysaccharides, made from one monosaccharide type, or heteropolysaccharides, containing different units. Starch and glycogen store glucose; their α-linked chains differ in branching, while cellulose has β(1→4) linkages and forms dietary fiber that humans cannot digest. Chitin is a structural polymer, and other heteropolysaccharides include dextran, agarose, glycosaminoglycans (GAGs), and peptidoglycan. GAGs contribute to extracellular-matrix hydration, elasticity, and signaling; heparin also has anticoagulant activity. Proteoglycans pair a core protein with GAG chains. Clinical connections include peptidoglycan as a target of β-lactam antibiotics and GAG accumulation in mucopolysaccharidoses. Together, these examples show how monomer type and glycosidic linkage relate to function.