A cell wall surrounds plant, fungi, bacteria, algae and archaea cells. It is a strong structure located just outside of the cells'cell membrane。植物细胞壁主要是由cellulose while fungi cell walls are composed of chitin, glucans and proteins and bacterial cell walls are mainly composed of peptidoglycan. However, all cell walls give the cell rigidity and strength, offering protection against mechanical stress and limit the entry of large molecules that may be toxic to the cell.