1. Osmosis

2. Experiment showing osmosis
What is osmosis?
What is water potential?
Water potential of sucrose solution
Water movement across a differentially permeable membrane
Osmosis and plant cells
Osmosis and red blood cells

3. Experiment showing osmosis
30 minutes later

4. What is osmosis?
The net movement of water molecules across a differentially permeable membrane from a less concentrated solution to a more concentrated solution
The net movement of water molecules across a differentially permeable membrane from a region of higher water potential to a region of lower water potential

5. What is water potential?
The probability of water molecules moving through a membrane from each side of the differentially permeable membrane
Value  as the concentration of solutes  (i.e. as the concentration of water molecules )
Distilled water: water potential = 0 greatest water potential
Solutions: water potential < 0 (-ve value)

6. - Water potential of sucrose solution ++ -
Water potential (arbitrary unit)
Concentration of sucrose solution (M)

7. Water movement across a differentially permeable membrane
low water potential
high water potential
net movement of water molecules
water molecule
sucrose molecule

8. Osmosis and plant cells
When young plant cells are immersed in
distilled water
 they become turgid, bigger and heavier

9. Osmosis and plant cells
When young plant cells are immersed in
concentrated sucrose solution
 they become soft, smaller and lighter

10. Osmosis and red blood cells
When red blood cells are immersed in
distilled water
they burst and release red pigments

11. concentrated sucrose solution
Osmosis and red blood cells
When red blood cells are immersed in
concentrated sucrose solution
they shrink

12. Summary
Osmosis: the net movement of water molecules across a differentially permeable membrane down a water potential gradient
Effect of osmosis