The cell wall is a layer of structure outside the cell membrane, the main component of the bacterial cell wall is peptidoglycan, the main component of the cell wall of plant cells is cellulose and pectin, and the main component of the cell wall of fungi is chitin. The main component of bacterial cell wall is peptidoglycan. Peptidoglycan is formed by n-acetylglucosamine and n-acetylcytidylic acid two kinds of aminosaccharides by β-1.4 glycosidic bond connection spacing arrangement of mechanical strong mesh structure. Plant cell wall consists of three parts, the main components are cellulose and pectin. It includes the intercellular layer, primary wall, and secondary wall. The main component of the intercellular layer is pectin. The primary and secondary walls are mainly composed of cellulose. The main component of the fungal cell wall is chitin, and the other components are cellulose, polysaccharides, and so on. The types of cell wall polysaccharides vary in different groups of fungi. The cell wall components of a fungus are not fixed, and the composition of the cell wall varies with the stage of growth.