Osmosis

the diffusion of water molecules across a selectively permeable membrane from a region of higher water potential to a region of lower water potential.

• the tendency of water to move to a lower concentrated area • measured in Kilopascals • pure water has a water potential of 0kPa - has the highest energy - highest tendency to leave

• measures how easily water moves out of a solution • as solute concentration increases the solute potential decreases - water is pulled in by the solute, and so becomes harder for the water molecules to leave.

• in plant cells only • is the pressure exerted onto the cell wall by the cell contents

• no cell wall • no pressure potential • water potential is equal to the solute potential