Download Osmosis in Cells - BIFS IGCSE SCIENCE

Osmosis in Cells
Some fab real time osmosis videos to
set the mood!
Group Starter Activity
Mr and Mrs Martinez went on holiday to Acapulco for a few days.
When they came back their favourite plant looked like this!
Explain the changes in terms of water movement
5 days ago
Today
Why is osmosis important?
Plants rely on the movement of water through them:
 Water always moves to areas of lower water concentration.
 Root hairs take in water from the soil by osmosis.
Plants- Water moving in
Water moves into a plant cell.
The cell wall stops the cell from bursting.
We say that the cell is turgid.
Turgid cell.
Vacuole is filling all the space and
pushing against cell wall
This is useful as it gives plant stems
support
Cell turgor pressure
Plants- Water moving out
When water moves out of the plant cell vacuole, by osmosis, it
becomes flaccid
Flaccid cell.
Vacuole is much smaller and
taking up less space
If a lot of water leaves the cell, the cytoplasm starts to peel away from the
cell wall and we say the cell has undergone plasmolysis.
Plasmolysis
Osmosis in Plant Cells
Low water
concentration outside
the cell
(ie concentrated
solution outside)
Equal water
concentrations inside
& out
(ie equal solute
concentrations
inside & out)
High water
concentration outside
the cell
(ie pure water or
dilute solution
outside)
Animals- Water moving in
Animal cells have no cell wall to stop the swelling, just a flexible
cell membrane.
If an animal cells are put in pure water (HWC) they take in water by
osmosis until they burst.
haemolysed
normal
turgid then burst
Animals- Water moving out
If an animal cells are put in a concentrated solution (LWC) they lose water
by osmosis until they become shrunken or haemolysed.
haemolysed
normal
http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/Osmosis_Anima
tion.htm
Quick Quiz- Osmosis
1.
What is a partially permeable membrane?
A membrane that only lets small molecules through it
2.
Which substance moves by osmosis?
Water, H2O
3.
What happens to plant cells that take up water by osmosis, and what do you call the
cell?
The cells become ‘full’ of water and are called turgid
4.
What happens to plant cells that lose water by osmosis, and what do you call the cell?
The cytoplasm comes away from the cell wall and the cells are
called plasmolysed.
5.
What does ‘haemolysed’ mean? How does it happen?
Animals cells which have lost water become shrunken and are
called haemolysed.
Now try your osmosis practice
problems!