Final answer:
Bacterial cell walls are composed of peptidoglycan, a polysaccharide that provides strength and shape to the cell.
Step-by-step explanation:
The major component of bacterial cell walls is called peptidoglycan, composed of long chains of alternating molecules of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). Peptidoglycan is a polysaccharide that provides the cell wall with tensile strength in two dimensions. It is unique to bacteria and is responsible for giving the cell its shape and protecting it.