3. A B
Balance the concentration on
both sides
If solute is of large molecules
Only water molecules can
diffuse through
In order to balance, we need
to add water on the more
concentrated side (B)
So, water molecules from A
(more dilute) will diffuse to B
(more concentrated)
Before After
A B A B
Water 10 5 5 10
Solute 5 10 5 10
4. A B
If solute is of small molecules
Both water and solute
molecules can diffuse through
the semi-permeable membrane
Diffusion of both molecules
occur until A and B are isotonic
Before After
A B A B
Water 11 5 8 8
Solute 5 11 8 8
5. By now, you should know that:
Movement of substances across plasma membrane
depends on the concentration of the solutions.
Water diffuse from more dilute solution (hypotonic) to
more concentrated solution (hypertonic).
6. Terms to take note and remember!!
Hypertonic – solution with higher concentration of
solutes than cell
Hypotonic – solution with lower concentration of
solutes than cell
Isotonic – solution of equal solute concentration with
cell
Which one has high solute concentration and low water
concentration? Hypertonic
The process where water diffuses across plasma
membrane from hypotonic soln. to hypertonic soln. is ...?
Osmosis
7. Effects of hypertonic, hypotonic & isotonic solutions on
plant cells
Hypertonic solution H2O diffuses out from cell by osmosis
H2O lost from vacuole & cytoplasm
Vacuole shrinks
Cytoplasm & plasma membrane shrinks and is
pulled away from the cell wall
Cell becomes flaccid. Plant wilts.
Process : Plasmolysis
If immersed in a hypotonic solution, H2O
diffuse into the cell, making it turgid.
Process : Deplasmolysis
8. Effects of hypertonic, hypotonic & isotonic solutions on
plant cells
Hypotonic solution
H2O diffuses into the cell by osmosis
Vacuole gains water, expands and exert
pressure outwards on the cell wall
This pressure (tugor pressure) causes the
cell to be turgid (firm)
Turgidity gives plant mechanical support
Isotonic solution No net movement of water across plasma
membrane
Water diffuses across the plasma membrane
at the same rate in both directions
Cell’s volume and shape maintains
9. Effects of hypertonic, hypotonic & isotonic solutions on
animal cells
Hypertonic solution
H2O diffuses out of cell by osmosis
H2O is rapidly lost
Red blood cells shrivel and probably die
Process : Crenation
Hypotonic solution H2O diffuses into the cell by osmosis
Red blood cells gain water and swell and
finally burst (because have no cell wall)
Process : Haemolysis
For other animal cells, the process is known as
lysis
10. Effects of hypertonic, hypotonic & isotonic solutions on
animal cells
Isotonic solution
No net movement of water across plasma
membrane
Water diffuses at the same rate in both
directions
Red blood cells maintain their shape
11. Hypertonic Isotonic Hypotonic
Flaccid No change Turgid
12. Osmosis in everyday life
1. Wilting plants
Excess use of chemical fertilisers which dissolve in
soil
Soil becomes hypertonic to the root cells
Water diffuses out from root cells into soil
Root cells becomes flaccid and undergo plasmolysis
Wilt and may eventually dies
2. Preservation of food
Salted fish
Preserved fruits