What is Selective Permeability?
In cell biology, selective permeability is the property of a living cell membrane that allows the cell to control which molecules can pass through the membrane, moving into or out of the cell. In order to understand cell membrane selective permeability, it helps to be aware that there are three different methods by which molecules can move into or out of cells. These three methods are passive transport, active transport, and transport by the use of vesicles. In passive transport across a selectively permeable membrane, molecules move across the membrane without the cell having to expend any extra energy. When water molecules move passively into or out of a cell, for example, this is called osmosis. Other small molecules may move across the membrane by the process of diffusion. This means that they move across the cell membrane from an area of high concentration to an area of low concentration. Oxygen molecules may diffuse from the lung cavity by passive transport into blood cells in th
