L.O:define L.O: to define diffusion and facilitated diffusion state to state factors affecting diffusion Starter: Starter: Recap on Osmosis a) What would happen to a red blood cell placed in a solution with low water potential (hypotonic)? b) What would happen to a plant cell placed in a solution with lower water potential (hypotonic)?

L.O:define L.O: to define diffusion and facilitated diffusion state to state factors affecting diffusion

Transport across the cell membrane All cells are surrounded by a partially-permeable membrane that controls what substances can enter and exit the cell. A cell needs to be able to import the substances it needs to survive, and to export waste materials and substances that are needed outside the cell. There are several methods by which substances (molecules and ions) can cross the cell membrane: diffusion osmosis active transport.

The movement of molecules or ions from a region of high concentration to a region of low concentration. It is a passive process, so requires no ATP (energy).

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Facilitated Diffusion? What on earth is it? Discuss in pairs

Facilitated Diffusion Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across a plasma membrane.

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L.O.2 Factors Affecting Diffusion There are 4 factors affecting diffusion You investigated one factor during the induction lesson back in July….! You have just seen another factor during the demo Think and discuss what the other two factors could be

Fick’s Law

Movement Across the Membrane DiffusionFacilitated Diffusion OsmosisActive Transport Direction along conc. gradient ATP (energy) needed? Carrier / channel proteins used? What is moved?

Movement Across the Membrane DiffusionFacilitated Diffusion OsmosisActive Transport Direction along conc. gradient Down ATP (energy) needed? No Carrier / channel proteins used? NoYesNo What is moved? Molecules Water