What major structural component is found in bacterial cell walls?

The major structural component found in bacterial cell walls is peptidoglycan. This unique polymer consists of sugars and amino acids that form a mesh-like structure, providing rigidity and strength to the cell wall. The sugars in peptidoglycan are often N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), which are alternately linked together to form long chains. These chains are then cross-linked by peptides, which contributes to the overall strength of the cell wall. This structural framework is essential for maintaining the shape of bacteria and protecting them from osmotic pressure, particularly in hypotonic environments.

Other options like cellulose and chitin are not involved in bacterial cell walls; cellulose is primarily a structural component of plant cell walls, while chitin is found in the exoskeletons of arthropods and the cell walls of fungi. Although proteins can be components of bacterial membranes and participate in various functions, they are not the primary structural component of the cell wall itself. Thus, peptidoglycan is distinctively important and specifically characteristic of bacterial cell walls, making it the correct answer.