The cell walls of archaebacteria are distinctive from those of eubacteria. Archaebacterial cell walls are composed of different polysaccharides and proteins, with no peptidoglycan. Many archaebacteria have cell walls made of the polysaccharide pseudomurein. The cell wall of archaea, as of any other prokaryote, is surrounding the cell outside the cytoplasmic membrane and is mediating the interaction with the environment. In this regard, it can be involved in cell shape maintenance, protection against virus, heat, acidity or alkalinity.