See also: Membrane (biology)

The plasmic membrane , or plasmalemme, delimits the cell, it separates the Cytoplasme from the external medium.

It is to be distinguished from the endomembranes which delimit the organoids.

Composed of Phospholipide S, proteins (which can be intracellular, extracellular or inserted in the double-layer phospholipidic) and of molecules of Cholestérol, it represents a barrier of very selective permeability. The plasmic membrane thus has the double role of protection and zone of exchanges between the intracellular and extracellular medium.

The plasmic membrane is a continuous film of 5 with 10nm thickness delimiting the cytoplasm of the extracellular medium. The membrane is formed by the association of two formed layers of phospholipides and glycolipides which faces by their hydrophobic pole. Between the molecules phospholipides molecules known as intrinsic and cholesterol are (only in the animals). On the faces external and intern, consisted the pole absorbent of membrane phospholipides, are fixed intrinsic proteins on which clings the cytosquelette or molecules of the substance (matrix) extracellular. Specificities of the membranes are especially due to the presence of the proteins which ensure the selective permeability, the recognition of chemical signals or carry markers (antigens of the CMH…). The majority of the components of the plasmic membrane are free and can move laterally. Membrane fluidity is all the more important as the fatty-acids constituting the membrane lipids are short and unsaturated.

Simple: Concealment membrane