- passive movement of molecules down a concentration gradient
- small uncharged molecules such as O2 and CO2
-can pass through phospholipids
Rate of diffusion depends on:
- Concentration gradient- larger the faster
- thickness of exchange surface - thinner the faster
- surface area - larger the faster
Diffusion of larger/charged molecules.
1) Carrier Proteins facilitate large molecules
- molecule attatches to protein which changes shape and releases on other side of membrance
2) Channel Proteins facilitate diffusion of charged particles
- via pores in the membrane
- different channel proteins for different charged particles
The diffusion of water moelcules across a partially permeable membrane from an area of high water potential to an area of lower water potential.
Water Potential: potential of water molecules to diffuse in or out of a solution
Isotonic: Same water potential