Osmosis video - Selective permeability of the cell membrane

The selective permeability of the cell membrane refers to the ability of the cell membrane to control the flow of substances in and out of the cell. It helps maintain a cell's internal environment, and to regulate its internal conditions, such as osmotic pressure, pH, and ion concentration. Movement across the cell membrane can occur by either passive transport, which requires no energy; or active transport, which requires energy in the form of adenosine triphosphate, or ATP for short.