Cellevegg

Cellevegg, or cell wall, is a rigid layer located outside the plasma membrane in most plants, algae, fungi, bacteria and some archaea. It provides structural support, helps determine cell shape, protects the cell, and constrains expansion during growth. Animal cells typically lack a cell wall.

In plants the cell wall is primarily made of cellulose, with a matrix of hemicelluloses and pectins. Primary cell walls are flexible while growth occurs; many plant cells develop a secondary cell wall inside the primary wall, often impregnated with lignin to increase rigidity in wood and other tissues.

Other organisms have different wall polymers. Bacteria use peptidoglycan, fungi use chitin, and certain archaea employ pseudopeptidoglycan or other polymers. The composition and structure reflect evolutionary adaptation and ecological niche.

The wall is permeable to water and small molecules and contains channels called plasmodesmata in plant cells, which traverse the wall and connect cytoplasm between neighboring cells. It also acts as a barrier to pathogens and mediates interactions with the environment. Growth is controlled by wall-loosening enzymes and turgor pressure.

Practical relevance: the cell wall is central to plant physiology, wood formation, and the textile and paper industries. It is a target for antibiotics in bacteria (peptidoglycan synthesis) and a focus of research in biofuels and fiber bioprocessing due to cellulose and lignin.