Cell Wall
The cell wall surrounds the cell membrane in bacteria, plants, some archae, fungi, and algae. Animalia cells and some protist cells (those not mentioned above) have only a cell membrane but no cell wall. The primary purpose of the cell wall is to provide structure and protect the protoplasm from damage caused by moving.
Plant cell walls provide rigidity to the cell, maintain cell shape, direct cell growth directions, and determine the architecture of the plant. It also prevents expansion when water is in the cell. Cell walls in plants are also used to store carbohydrates (they are primarily a carbohydrate polymer called cellulose) and protect from disease. Neighboring cells are bound together with the middle lamella, a gelatinous extracellular membrane. In some plants, a secondary cell wall is formed below the primary one, providing even more structure.
Algal cell walls are also heavy in cellulose and glycoproteins, but also include some polysaccharides not found in plants, like agarose and carrageenan. Diatom algae include silicon (in the form of silicic acid) in their cell walls.
Bacterial cell walls are used mostly for protection against environmental hazards (like the human immune system). Peptidoglycan, a primary component of these walls, is the substance detected for in Gram staining. Penicillin and other similar antibiotics target the bacterial cell wall. Fungal cell walls are similar to plant cell walls in that they contain cellulose, but they also contain glucosamine and chitin, both common supplements in herbal remedies for arthritis.
Web Resources On Cell Wall
Plant Cell Wall
The Cell Wall
Book Resources On Cell WallFungal Cell Wall: Structure, Synthesis, and Assembly by Jose Ruiz-Herrera
The Plant Cell Wall by Jocelyn K. C. Rose
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