This document summarizes osmosis and the effects of hypertonic, hypotonic, and isotonic solutions on plant and animal cells. It explains that in a hypertonic solution, water diffuses out of the cell, while in a hypotonic solution water diffuses into the cell. An isotonic solution does not change the cell volume as water diffuses in both directions at equal rates. It provides examples of how osmosis impacts wilting plants and food preservation.

1. Diluted sugar Concentrated
solution sugar solution

2. Hypotonic solution Hypertonic solution

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