4 1 CELL BIOLOGY LESSON 9 Learning objective

4. 1 CELL BIOLOGY LESSON 9

Learning objective: All students: Produce a hypothesis based on prior knowledge of osmosis and plan a reliable investigation that can be used to test the effects of osmosis.

What is Osmosis? The movement of water from high to low concentration through a partially permeable membrane What is a partially permeable membrane A membrane that has small holes in it & only lets small water molecules move through it. It does not let large solute molecules through. What is the partially permeable membrane in the cell? The cell membrane

NEW KEY TERMS! Isotonic solution – the solution has the same solute concentration as the inside of the cell Hypertonic solution – the solution has a higher solute concentration than the inside of the cel Hypotonic solution – the solution has a lower solute concentration than the inside of the cell

OSMOSIS AND PLANT CELLS Flaccid – Plasmolysed! Wilting plant W I L T I Turgid Upright plant

PLASMOLYSIS IN ONION CELLS

TURGID ONION CELLS

PLANT CELLS cell wall vacuole The cell absorbs water by osmosis. . cytoplasm and cell membrane . . but the cell wall stops the cell expanding any more

• ANIMAL CELLS DON’T HAVE A CELL WALL • THIS MEANS THEY EITHER: • SWELL AND BURST IF WATER OSMOSES IN • SHRINK IF TOO MUCH LEAVES Can no longer carry blood around body