Water Potential

• Osmosis is quantified using water potential (Ψ: the tendency for water molecules to diffuse from one solution to another (Formula: Ψ = Solute Potential + Pressure Potential)
• Polar solute’s presence restricts water movement as the water molecules, cluster around the solute particles; less ‘free’ water molecules left, able to diffuse from one solution to another
• Cells water potential is lower than pure waters (Pure Water = 0kPa); solutes dissolved in the cytoplasm, in plant cells, the large vacuole also contains solutes
• All solutions have a negative Ψ, the more solute, the more negative, also all cell membranes are selectively permeable; water always diffuses in/out of organelles/cells by osmosis, down a water potential gradient