Osmosis in Cells

1. Osmosis in Cells Some fab real time osmosis videos to set the mood!

2. 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

3. 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 byosmosis.

4. 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

5. Cell turgor pressure

6. Plants- Water moving out Flaccid cell. Vacuole is much smaller and taking up less space When water moves out of the plant cell vacuole, by osmosis, it becomes flaccid 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.

7. Plasmolysis

8. Low water concentration outside the cell Equal water concentrations inside & out High water concentration outside the cell (ie pure water or dilute solution outside) (ie concentrated solution outside) (ie equal solute concentrations inside & out) Osmosis in Plant Cells

9. Animals- Water moving in If an animal cells are put in pure water (HWC) they take in water by osmosis until they burst. Animal cells have no cell wall to stop the swelling, just a flexible cell membrane. haemolysed normal turgid then burst

10. If an animal cells are put in a concentrated solution (LWC) they lose water by osmosis until they become shrunken or haemolysed. Animals- Water moving out haemolysed normal http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/Osmosis_Animation.htm

11. Quick Quiz- Osmosis • What is a partially permeable membrane? • Which substance moves by osmosis? • What happens to plant cells that take up water by osmosis, and what do you call the cell? • What happens to plant cells that lose water by osmosis, and what do you call the cell? • What does ‘haemolysed’ mean? How does it happen? A membrane that only lets small molecules through it Water, H2O The cells become ‘full’ of water and are called turgid The cytoplasm comes away from the cell wall and the cells are called plasmolysed. Animals cells which have lost water become shrunken and are called haemolysed.

12. Now try your osmosis practice problems!