1. Membrane Transport AS Biology

2. Diffusion Powered by random movement of molecules in a solution Net movement is from regions of high concentration to low. The diffusion concentration is called a CONCENTRATION GRADIENT http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__how_diff usion_works.html

3. The amount of movement is proportional to the concentration difference and the permeability of any barrier like a membrane. What speeds up diffusion? Small particles Thin membrane Large surface area Short distance Increase in temperature

4. Facilitated diffusion A passive process (does not require energy!! (ATP)) 1. Channel Proteins Eg. Na + K + Cl - (polar molecules and usually specific for one type of ion)

5. 2. Carrier proteins Proteins act as carriers or pores permit flux of substances that cannot diffuse directly through the membrane. http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.htm lhttp://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.htm l

6. Diffusion of water down its concentration gradient is called Osmosis. http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html Osmosis is the movement of water molecules across a partially-permeable membrane down a water potential gradient. More specifically, it is the movement of water across a partially permeable membrane from an area of high water potential (low solute concentration) to an area of low water potential (high solute concentration).water potential solute

7. http://bcs.whfreeman.com/thelifewire/conte nt/chp05/0502001.htmlhttp://bcs.whfreeman.com/thelifewire/conte nt/chp05/0502001.html