BIOL 1F90 Lecture Notes - Lecture 11: Lipid Bilayer, Scanning Electron Microscope, Facilitated Diffusion
25 Oct 2016
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Document Summary
Permits visualization of the surface of membranes. Samples are frozen in liquid nitrogen and than fractured. Membranes located in the fractured region may split along their leaflets (peel apart) Sample is sprayed with a heavy metal and viewed with scanning electron microscope. If plasma membranes were composed of only phospholipids, transport would be limited: phospholipid bilayer is almost impenetrable. Substantial amounts of proteins create a membrane that is selectively permeable: especially trans membrane proteins, sele(cid:272)ti(cid:448)e (cid:271)e(cid:272)ause proteins don"t just allo(cid:449) anything through. Membrane structure ensures: essential molecules enter. Do not leave cell because not allowed out: waste products exit. Diffusion: movement of a solute from a region of high concentration to a region of lower concentration: amphipathic. Rate of passive diffusion through a phospholipid bilayer is about 50 times higher even though it is a little larger. Ca2+ not able to move through mebrane hydrophilic.
