BISC306 Lecture Notes - Lecture 2: Lipid Bilayer, Cell Membrane, Alpha Helix
14 Sep 2016
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Document Summary
Membranes-biological membranes, cell membranes, plasma membrane: 1) fluid activity, 2) phospholipid bilayer-50% lipids. Limited permeability to ions & large polar substances. Permeable to water & small uncharged solutes. Permeable to hydrophobic solutes; but have problem getting to and from membrane. Co2 and oxygen-small, uncharged, nonpolar gases; easily move in and out of cell. Urea & glycerol-small enough to get across membrane: 3) protein composition-50% proteins, nonpolar-hydrocarbons; hydrophobic (such as steroids, cholesterol-as hydrophobic lipid steroid; helps cell change shape and be fluid according to temperature of situation. Transportation of molecules: simple diffusion, diffusion-random movement of particles without energy/atp a. i. Fick diffusion equation-determines rate of diffusion a. i. 1. a. i. 2. J=rate of diffusion; c1 and c2=concentrations of solutions; d=difference coefficient; x=distance a. i. 3. a. i. 4. Very efficient @ short distances; movement of uncharged solutes by simple diffusion across a semipermeable membrane: water movement b. i. Proteins-make up channels and carriers; often specific & gated b. i. 1. 4 different domains: channel through membranes b. i. 2. b. i. 3. b. i. 4.
