Diffusion & Osmosis

• 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