The bacterial cell wall is a rigid structure that surrounds the cell membrane of bacteria, providing shape and protection. It is primarily composed of a polymer called peptidoglycan, which consists of sugars and amino acids. This wall helps maintain the cell's integrity, preventing it from bursting in hypotonic environments. There are two main types of bacterial cell walls: Gram-positive and Gram-negative. Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner layer and an additional outer membrane. The differences in cell wall structure are important for antibiotic effectiveness and bacterial classification.