BIOL 300 Lecture Notes - Lecture 19: Lipid Bilayer, Facilitated Diffusion, Glycerol
Document Summary
Size and charge matters when molecules diffuse across the lipid bilayer. Non polar molecules such as o2 can go through and co2 which can dissolve in the hydrophobic interior can go through as well. Hormones and drugs can also go through. Very small uncharged molecules such as h2o or glycerol can go through as well. Charged molecules such as cl- cannot go through. Their charge and hydration shell makes the bilayer even more impermeable to these ions and molecules. Metabolic processes require the molecule and ions that take a very long time to passively diffuse therefore the protein complexes that span the bilayer help move them across the membrane. Concentration gradient needs to be present still and if the gradient is at 0 then the diffusion won"t occur. Two groups of transport proteins carry out facilitated diffusion: For facilitated diffusion integral membrane proteins (or transport proteins) are used that span the membrane.
