Plasma Membrane

The plasma membrane is a double-layered structure that surrounds the cell. It provides a boundary between the cell and its environment. In animal cells, it is outside the cell border. In plant cells, it is located inside the cell wall. It's function is to control the passage of materials into and out of the call and to help maintain its shape. The plasma membrane is selectively permeable, which means it lets some materials into the cell while keeping others out.