The natural polymer made from repeating glucose units in plant cell walls is cellulose.
Cellulose consists of long chains of β-D-glucose molecules joined by β(1→4) glycosidic bonds. These straight chains form strong hydrogen-bonded fibers, giving plant cell walls much of their mechanical strength. Cellulose is the most abundant organic polymer on Earth.
Humans cannot digest cellulose because human digestive enzymes do not break its β(1→4) linkages. It nevertheless provides dietary fiber and is important in paper, cotton, textiles, cellophane, and many biomaterials. Wood contains cellulose together with lignin and hemicellulose.
Starch also consists of glucose units but mainly uses α linkages and serves as a plant energy store. Glycogen is the principal storage polysaccharide in animals and fungi. Chitin is a nitrogen-containing polymer found in arthropod exoskeletons and fungal cell walls.