soluseinämä

Soluseinämä, or cell wall, is a rigid layer surrounding the plasma membrane of most plant, fungal, bacterial, algal, and some archaeal cells. It provides mechanical support, determines cell shape, protects against mechanical and osmotic stress, and mediates interactions with the environment. Because its composition varies between organisms, the term encompasses several distinct structural types.

In plants and many algae, the cell wall is primarily made of cellulose fibers embedded in a matrix of hemicelluloses and pectins. Plant cells typically have a primary wall that expands during growth and, in many cells, a thicker secondary wall reinforced with lignin. The space between adjacent cells is filled by the middle lamella, rich in pectins, which glues cells together and allows plasmodesmata to connect cytoplasm across cell walls.

In bacteria, the wall consists mainly of peptidoglycan. The layer is thick in Gram-positive bacteria and thinner with an outer membrane in Gram-negative bacteria. Teichoic acids may be present in some Gram-positive walls. The bacterial wall provides shape and rigidity and is a common target for antibiotics such as beta-lactams; lysozyme can degrade peptidoglycan.

In fungi, the wall is primarily composed of chitin and glucans, along with glycoproteins. This composition gives structural integrity and protects against osmotic stress in fungal cells.

Other examples include diatoms with silica-based walls and certain algae with alginates or other polymers. Soluseinämä is dynamic, changing during growth and development, and plays a central role in physiology, ecology, and biotechnological applications.