Kohdemembranin

Kohdemembranin is a German term that translates to "outer membrane" in English. This biological structure is a defining characteristic of Gram-negative bacteria. Unlike Gram-positive bacteria which possess a thick peptidoglycan layer and an inner plasma membrane, Gram-negative bacteria have a more complex cell envelope. The outer membrane is the outermost layer of this envelope, lying external to the peptidoglycan layer.

The kohdemembranin is a lipid bilayer that is asymmetrically structured. The inner leaflet of the outer membrane is primarily composed of phospholipids, similar to the plasma membrane. However, the outer leaflet is characterized by the presence of lipopolysaccharides (LPS). LPS is a complex molecule consisting of three parts: lipid A, a core polysaccharide, and an O-antigen. Lipid A is embedded in the outer membrane and is responsible for its endotoxic properties. The core polysaccharide links lipid A to the O-antigen, which is a variable, repeating polysaccharide chain that extends outwards from the cell surface and plays a role in antigenicity and interaction with the environment.

Embedded within the kohdemembranin are various proteins, including porins. Porins are pore-forming proteins that create channels through the outer membrane, allowing for the passive diffusion of small hydrophilic molecules, such as nutrients and waste products, into and out of the cell. Other proteins in the outer membrane include transport proteins, enzymes, and structural proteins. The kohdemembranin acts as a barrier, protecting the bacterium from harmful substances, such as detergents and certain antibiotics, while still permitting the passage of essential molecules.