Presentation on theme: "7-3 Movement through the Membrane"— Presentation transcript:
1 7-3 Movement through the Membrane The cell membrane is semipermeable- only certain molecules can get throughPassive transport: no energy required1. Diffusion: the movement of molecules from a region of high concentration to a region of low concentration
2 - continues until equilibrium is reached (equal concentrations on both sides of membrane)
3 - temperature affects diffusion: higher = faster- size of particles affects diffusion:smaller = faster
4 2. Osmosis: the diffusion of water. across a membrane from high water 2. Osmosis: the diffusion of water across a membrane from high water concentration to low water concentration97% water100% waterWhich way will the water move?
5 97% water90% waterWhich way will the water move?
6 This solution is hypertonic - water diffuses out of the cell This solution is hypotonic- water diffusesinto the cell
7 This solution is isotonic - no net change 95% waterThis solution is isotonic- no net change
8 3. Facilitated diffusion: uses protein channels to move molecules from high concentration to low concentrationActive Transport: energy required1. Carrier proteins may act as pumps-example: sodium-potassium pumpa. Cells continually pump potassium ions into the cell, and sodium ions out
9 Important for muscle contraction and nerve impulse transmission K+