Osmosis occurs when a solvent moves through a semi-permeable membrane to dilute a solute that is not able to permeate the membrane. The process is essential for the transport of water across biological membranes in living organisms.
In the process of osmosis, a less concentrated solvent moves through a semi-permeable membrane into a more concentrated solvent. The most common solvent is water. In animal cells, salt is not able to move in or out of the cellular membrane. In order to maintain the cell's health, water moves in and out of the cell through the process of osmosis, diluting the cellular salt level.
The process of osmosis can be observed during the rehydration of dried fruits and vegetables. While plant cells are not identical to animal cells, both cell types have a semi-permeable cell wall or membrane. After placing a dehydrated piece of fruit into a bowl of water, there is a change in the fruit as the water permeates the cell walls. Prior to the process of osmosis, the dehydrated fruit has a large concentration of sugars. Once water permeates the cell walls, re-hydrating the fruit, the sugars in the fruit are less concentrated. Through osmosis, a state of equilibrium is achieved.