It is because these structural polysaccharides exist as sets of long strands that are linked to one another. They form fibers that give cells strength and elasticity. Cellulose and chitin are homopolysaccharides meaning that they contain only a single type of monomeric unit, while peptidoglycan is built from two alternating monosaccharide units. Cellulose is found in plant cell walls and chitin is a structural component of animal exoskeletons. Peptidoglycan forms the rigid layer of the bacteria’s wall.