Cellulose, a linear polysaccharide, is a major structural component in plant cell walls. Comprising repeating glucose units linked by β-1,4-glycosidic bonds, cellulose forms long, unbranched chains. The β-linkages create a straight and rigid structure, allowing cellulose molecules to align in parallel, forming strong, insoluble fibers. This characteristic enhances its role in providing structural support to plant cells. Cellulose is resistant to digestion by most animals due to the lack of enzymes capable of breaking β-bonds. Instead, certain microorganisms and herbivores possess specialized enzymes, like cellulases, enabling them to extract energy from cellulose.