A permeable membrane lets everything through, similar to how you let everyone into your home for the block party. An example of a permeable membrane in nature is the cell wall in plant cells. Cell walls provide support and protection for plant cells. They are fully permeable to water, molecules, and proteins. This allows water and nutrients to be freely exchanged between the plant cells. If you look at this diagram of the permeable membrane, both the large circles and the small stars can freely move across.
Semi-Permeable MembraneCell membranes are semi-permeable. Just like your private dinner party, only certain molecules can cross the cell membrane. This allows the cell some control over what enters and leaves. Water, small molecules, and molecules without a charge can pass freely. Large molecules and strongly positively or negatively charged molecules must stay outside. Impermeable membrane An impermeable membrane is one through which no substance can pass. Mitochondrial walls are example of impermeable membrane