Polysackarider

Polysackarider, or polysaccharides, are long carbohydrate polymers made up of repeating monosaccharide units joined by glycosidic bonds. They vary widely in monomer type (homopolysaccharides versus heteropolysaccharides), linkage patterns, degree of branching, and molecular weight. Their structure determines properties such as solubility, viscosity, and gel formation, which in turn influence their biological and industrial roles.

They are broadly categorized by function. Energy storage polysaccharides include starch in plants and glycogen in animals, both composed primarily of glucose with alpha linkages; starch contains linear amylose and branched amylopectin, while glycogen is highly branched. Structural polysaccharides provide support and protection, such as cellulose in plant cell walls (beta-1,4 linkages) and chitin in arthropod exoskeletons and fungal cell walls (also beta-1,4, with N-acetylglucosamine units). Other important polysaccharides include pectins, agar, alginates, and dextrans, which can serve as extracellular matrices or food-related thickeners.

In nutrition, some polysaccharides are readily digested (for example, starch and glycogen by human amylases) to yield sugars for energy. Others are resistant to digestion and function as dietary fiber, contributing to gut health through fermentation by microbiota and production of short-chain fatty acids. Industrially, many polysaccharides are valued as thickeners, gelling agents, stabilizers, or films, with applications in food, pharmaceuticals, and materials science.

Biosynthesis occurs via glycosyltransferase enzymes that assemble activated sugar donors into polymers, a process occurring across plants, animals, bacteria, and fungi. The physical and chemical properties of polysackarider products reflect their monomer composition, linkage types, branching, and length.