Cell Wall vs Plasma Membrane
All organisms are made up of cells. Depending on the cellular organization organisms could be categorized as prokaryotes (bacteria and archea) and eukaryotes (fungi, plants, animals). All of them have plasma membranes, but cell wall is not present in all. Among the species which have a cell wall differences lie in the type of the cell walls and the contents depending on the type of organism.
A wall is a protective layer. A cell wall equally is a protective layer for the cell. It is an additional barrier which is situated at the most outside layer of a cell. Prokaryotes e.g. bacteria, fungi, and plants have cell walls. Humans and any other species belonging to the animal kingdom do not possess cell walls. Cell wall provides protection. In bacteria, it is comprised of peptidoglycan a slimy layer rich in carbohydrates and protein. Since most bacteria are subjected to harsh environmental conditions, it protects the bacteria, and it is also one reason that our body defenses sometimes cannot fight bacterial infections. The fungal cell wall constituent is called chitin a carbohydrate polymer.
In plants, it is different. The cell wall is a rigid structure built up of 3 layers. Middle lamella is a layer rich in pectin and the primary and secondary cell walls contain cellulose, hemi cellulose and lignin respectively. Once lignin is incorporated the cells are impermeable to water thus they die. It is found in xylem the tube like structures transporting water inside a plant. The plant cell wall also allows withstanding osmotic pressure. It is the reason why plant cells do not burst after taking in too much water.
Plasma membrane/cell membrane is the biological membrane which separates inner cell contents from the outer environment. It is not a rigid barrier but a very intelligent border which allows necessary material to come, to eliminate waste, and to communicate between tissue and cells. Cell membrane is mainly made up of phospholipids. These have a polar head and a non polar fatty tail. Therefore, they make a bi-layer where the polar heads are facing opposing sides (looking like a sandwich). In certain places, there are proteins embedded and on the layer facing outside some carbohydrates are attached to the surface. This model is called the “Fluid mosaic model” because the structure is flexible and mosaic due to various components. The main functions of the plasma membrane are cell adhesion, ion conductivity, cell signaling, osmosis, endocytosis, and exocytosis.
What is the difference between Cell Wall and Plasma Membrane?
• Cell wall is limited to some organisms like fungi, bacteria and plants, but plasma membrane is a universal cell component present in almost all organisms.
• The components and structure of the cell wall and plasma membrane are different. Cell wall in bacteria is made up peptidoglycan, in fungi it is made up of chitin and in plants cellulose, hemi cellulose, and lignin. But plasma membrane is made up of phospholipids arranged in a bi-layer.
• Cell wall and plasma membrane cater to different functions.