Which polysaccharide has the main function of being a structural component of bacterial cell walls?

The correct answer is peptidoglycan

Explanation:

Peptidoglycan is the polysaccharide that has the main function in making the structural component of the bacterial cell wall. Gram-positive bacteria have a cell wall made up of purely peptidoglycan layer but in gram-negative bacteria, a thick outer covering of lipopolysaccharide is also present.

Peptidoglycan is made up of NAG (N-acetyl glucosamine) and NAM (N-acetyl muramic acid) unit which are joined by β 1-4 glycosidic linkage. Lysozyme is the enzyme which breaks this linkage and destroys the bacterial cell wall.

Due to outer thick peptidoglycan layer, gram-positive bacteria retain crystal violet stain and appear blue in color after gram's staining while gram-negative bacteria do not have outer thick peptidoglycan layer, therefore, it gets destain and get counterstain by safranin and appears pink.