Cell wall of Gram −ve bacteria is thin (10−15nm) and hard and is not destroyed by penicillin, whereas cell wall of Gram +ve bacteria is thick (25−30nm) and is destroyed by penicillin. Cell wall of Gram −ve bacteria is less homogenous, more complex and multilayered. Lipids (including phospholipids, lipopolysaccharides and lipoproteins) make up 80−85% of the total cell wall. Teichoic acids are absent in Gram −ve bacteria. Presence of lipopolysaccharides in cell wall of Gram−ve bacteria makes them more resistant and pathogenic.