 Recap on osmosis as a special type of diffusion of water.  Understand the function of xylem and phloem  Understand how water acts against gravity  Know how plants get minerals against concentration gradients.  Transpiration  Active transport  Xylem  Phloem

 Osmosis is very similar to diffusion but ONLY talks about the movement of water particles Osmosis is the diffusion of water molecules from an area of high concentration to an area of low concentration across a partially permeable membrane

 tw tw  Watch the video and you must explain why the egg changes using what you understand of osmosis  Write two explanations. One for the corn syrup, the other for pure water.

In the corn syrupIn the pure water  Water moves from the higher concentration in the egg yolk to the lower water concentration in the corn syrup. (1)  Across a partially permeable membrane (1).  The partially permeable membrane has pores that allow the movement of water but not the sugar molecules (1).  Water moves from the higher concentration of water to the lower concentration of water in the egg yolk (1).  Across a partially permeable membrane (1).  Quality of written communication (1)

The cell membrane separates the contents of the cell from the outside It has tiny holes in it This allows small molecules to pass through it but not large molecules It is PARTIALLY PERMEABLE

Osmosis occurs across a semi permeable membrane which has tiny holes in it. These holes are small enough for water molecules to pass through but larger molecules cannot pass through Water molecules = Squash molecules =

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

 Flaccid (plasmolysed) Turgid Wilting plant upright plant

 Animal cells don’t have a cell wall  This means they either: ◦ Swell and burst if water osmoses in ◦ Shrink if too much leaves Why might water leave or enter the cell in each case??

Can no longer carry around body

cell wallcytoplasm and cell membrane vacuole The cell absorbs water by osmosis but the cell wall stops the cell expanding any more Plant cells

OsmosisWhen water enters a plant cell and pushes on the cell wall causing the cell to swell TurgidA membrane that allows some substances to pass through and others cannot. PlasmolysedThe movement of particles from an area of high concentration to an area of low concentration Partially permeable The movement of water molecules from an area of their high concentration to an area of their low concentration DiffusionWhen water leaves a plant cell, the cell contents shrink and the cell membrane pulls away from the cell wall

XylemPhloem  Dead tissue  Transports water and dissolved minerals  Living tissue.  Transports sucrose (glucose from photosynthesis is converted into sucrose)

Xylem tissue is found in the vascular bundle in the stem. It is also found throughout the plant. Phloem tissue is found in the vascular bundle in the stem. It is also found throughout the plant.

 hk hk  What causes water molecules to stick together and what is this force called?  What happens when a water molecule evaporates?  Why does water not just fall down the xylem?  What conditions increase transpiration and why?  Why do plants wilt?

 Most minerals in the soil are in low concentration.  Active transport pumps are proteins that use some of the plants energy to bring mineral ions into the root.  Explain using the term osmosis why active tranport is needed to draw in some minerals.