What is Wall, Cell?

In most algae, bacteria, and fungi, the structure which forms a (usually rigid) layer external to the CELL MEMBRANE and which is responsible for the shape of the organism and for protecting it from mechanical damage, osmotic lysis, etc. It may also serve as a permeability barrier, e.g., to antibiotics and other substances. (Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)