Cell walls can be similar to waste container, while cell membrane can be considered as waste bag. Cell walls can also be considered similar to a brick wall that provides support and protection. The structure of cell walls varies from species to species, hence, if plant cell walls are built from a structural carbohydrate, called cellulose, bacteria or fungi cell walls are built from a structural carbohydrate, called chitin. While cellulose is a special sugar that, unlike glucose, is not water soluble, chitin, is a protein. Both, cellulose and chitin, provide important properties to the cell walls, such as flexibility, elasticity and resistance.
Cell walls have holes in their structure, called plasmodesmata. These holes allow the connection between membranes of different cells. The connection between membranes makes possible the transfer of nutrients between cells.