Which macromolecule is a primary component of the bacterial cell wall?

The primary component of the bacterial cell wall is peptidoglycan. This macromolecule is crucial for maintaining the structural integrity and shape of bacterial cells. Peptidoglycan consists of a mesh-like polymer made of sugars and amino acids, which forms a rigid layer outside the plasma membrane. This structure provides protection against osmotic pressure, preventing the cell from bursting in hypotonic environments, and also contributes to the overall resistance of bacteria to physical stresses.

In contrast, cellulose and chitin are polysaccharides that serve structural roles in plants and fungi, respectively, but are not found in bacterial cell walls. Starch serves primarily as an energy-storage polysaccharide in plants and is not a structural component of bacterial cells. Peptidoglycan is unique to bacteria, which is why it is a key target for antibiotics and plays a significant role in the classification of bacterial species based on cell wall structure, such as Gram-positive and Gram-negative bacteria.