BRAINCAKEOsmotic Potential (π)
Osmotic potential (π) is the part of water potential that is due to dissolved solutes. It is now usually called solute potential, written ψs. Both names describe the same idea: how much the solutes lower the water potential.
Solute molecules attract water molecules, so fewer water molecules are free to move. This lowers the tendency of water to leave the solution. So:
• pure water has a solute potential of 0 kPa;
• any solution has a solute potential below zero, so solute potential is always zero or negative;
• the more solute dissolved, the more negative the solute potential.
Solute potential depends on the number of dissolved particles, not their type. A solution of salt that splits into two ions has a more negative solute potential than a sugar solution of the same molar concentration.
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Key terms in this lesson
- water potential
- A measure of the tendency of water molecules to move out of a solution; water moves from a higher to a lower (more negative) water potential.
More in Cell Transport Mechanisms
- Osmosis in Animal Cells
- Water Potential in Plant Cells
- Osmosis in Plant Cells
- Turgor Pressure (P)
- Water Potential, Turgor Pressure and Osmotic Potential
- Active Transport
- Evidence for Active Transport
- Endocytosis and Exocytosis
All 18 lessons in Cell Transport Mechanisms · All Edexcel AS-level Biology topics