Cell membrane

Definition

The cell membrane (also called the plasma membrane, cytoplasmic membrane, or plasmalemma, and abbreviated as PM) is a thin membrane completely surrounding the cell. It comprises a lipid bilayer. It controls the entry and exit of materials relative to the cell, and also the interaction and signals between the cell and its environment.

Summary

Item	Value
Type of organisms whose cells contain cell membranes	All organisms; see all cells have cell membranes
Type of cells within the organisms that contain cell membranes	All cells; see all cells have cell membranes
Number of cell membranes per cell	1; there's just one cell membrane enclosing the cell
Shape	The shape is the same as the shape of the cell.
Size	The cell membrane is about 5-10 nm (50-100 angstrom) thick. This is typical for lipid bilayers.
Location within cell	The cell membrane is the boundary of the cell, enclosing it from all sides.
Chemical constituents	Lipids, phospholipids, carbohydrates, proteins
Function	Control of the entry and exit of materials as well as signals from the environment to the cell