Osmosis is a special case of diffusion in which water moves from a solution of higher water potential to a solution of lower water potential through a partially permeable membrane. Recall of isotonic will be expected.

Osmosis is a similar movement to diffusion, however given concentration is how much of something is dissolved in water, it is not talked about in terms of concentration. Instead we talk about water potential (Ψ)- referring to how much is dissolved in the water.

0Ψ is pure water, it has nothing dissolved in it. The lower the water potential, the more things dissolved in it. -1Ψ is water with some impurities, -2Ψ has more e.c.t.

Water will move from areas with a high water potential, to areas with a lower water potential, through membranes that are semi-permeable (allow some things through.)

An isotonic solution is one with the same things and amounts dissolved in it as there are inside cells. Cell tissue is isotonic; this means that it will have the same water potential as the cell, and water will not move out of the cell- dehydrating it- or into the cell- bursting it.