Cytoplasmic Membrane
Made of a phospholipid bilayer with integral and peripheral proteins embedded. It maintains the selective permeability of the cell, has respiratory enzymes and during cell division the chromosome is linked to the cell membrane at a site called Mesosome. 

Cell Wall

Protects and maintains the shape of the organism. 
There are 2 basic cell walls, Gram positive and Gram negative. 

Gram Positive:

Has a thick peptidoglycan (murein) layer and 2 classes of teichoic acids. Lipoteichoic acid which is on the surface, embedded in the peptidoglycan layer and is linked to the cytoplasmic membrane. Wall teichoic acid is on the surface and is linked to only the peptidoglycan layer. Teichoic acid is responsible for the antigenic determinant of the organism.


 
 

 Gram Negative

Has a thin peptidoglycan (murein) layer with an outer membrane attached to the peptidoglycan layer by lipoproteins. The outer membrane is made of protein, phospholipid and lipopolysaccharide. In the lipopolysaccharide, the lipid portion is embedded in the phospholipid and the O antigen polysaccharide is on the surface. The lipid is called Lipid A and it is toxic, but the whole lipopolysaccharide is called an Endotoxin. The cell wall has channels called Porins for the transport of low molecular weight substances. Between the cytoplasmic membrane and the cell wall is a periplasmic space with hydrolytic enzymes, antibiotic inactivating enzymes and transport proteins.


Copyright 1996 by the Faculty Resource Center
Sylvester McKenna & Devabrata Mondal
Long Island University, Brooklyn Campus