Final answer:
The cell wall is a rigid structure composed mostly of peptidoglycan in bacterial cells, providing shape, protection, and rigidity to the cell.
Step-by-step explanation:
The structure being described is known as the cell wall, which is a rigid layer that surrounds the cells of bacteria and other organisms, including plants and fungi. In bacterial cells, the cell wall is primarily composed of peptidoglycan, a substance made up of long chains of polysaccharides that are cross-linked by peptides, forming a strong and protective mesh-like layer. This layer provides protection against osmotic lysis and contributes to maintaining the cell's shape and rigidity. The presence of the cell wall is crucial, as it allows bacteria to withstand the high osmotic pressure within their cytoplasm. In addition to peptidoglycan, other major polysaccharides such as cellulose, hemicellulose, and pectin are found in the cell walls of plants. Some antibiotics target the bacterial cell wall, disrupting its formation and effectively killing the bacteria.