|Class 9 Biology Fundamental Unit of Life||Plasma membrane|
Plasma membrane is the outermost layer in cells.
It separates the content of cell from their external environment.
It allows the materials from surrounding to enter and exit the cell. It also allows the materials from cell to exit outside.
It controls the entry and exit of materials in nd out of cell and hence it is called selectively permeable membrane.
Gases like carbon-dioxide or oxygen can also move in or out from high concentration to low concentration in a cell through the cell membrane by the process of diffusion.
It also allows the movement of water in and out of the cell depending upon the concentration outside the cell by the process of osmosis.