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Unformatted text preview: Cell Membrane Overview- Phospholipid bilayer- Gases and lipid-soluble molecules diffuse thru readily- Impermeable to organic anions (i.e. proteins)- Permeability depends on molecular size, lipid solubility and charge- Water diffuses thru aquaporin channels- Fluid Mosaic Model of Cell Membrane Membrane Lipids Polar end (hydrophilic): glycerol + phosphate + choline/serine/etc. Non-polar end (hydrophobic): normally 1 fatty acid (FA) tail is saturated, other polyunsaturated-> Cholesterol inserted among FA chains Membrane Fluidity : to remain intact and exible- Mechanical properties of membrane determined by lipid composition- Essential for efcient carrier and channel protein fxn- Cholesterol stabilizes membrane & prevents diffusion of polar molecules across it. - Reduced by agin & poor diet (FA sourced from food) Membrane Proteins- Structural support for cytoskeleton- Transmembrane (TM) channels for diffusion of selected molecules/ions- Selective transporters (carriers) of molecules across membrane- Enzymes/ion pumps for active transport- Receptors for signaling molecules (part of endocrine system) Membrane-spanning proteins: diagram- Crossing membrane 7x common: one end of peptide chain on either side- Sections of protein crossing membrane usually are helical, and outside the membrane, sections are usually beta sheets F5-2 F5-5 PSL302: Lecture 01, by Prof. MacKay Monday, Sept. 13, 2010 1 of 5 Glycocalyx- Matrix of long carb Flaments that Fll extracellular space (ECS, or for uid), slowing down diffusion of molecules into cell (cells fur coat)- Anchored to membrane proteins (glycoproteins) or lipids (glycolipids)- Contain hyaluronic acid & chondroitin sulfate- Net -ve charge: attracts & sequesters Ca 2+ on carb Flament...
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This note was uploaded on 03/27/2012 for the course PSL PSL300 taught by Professor Mackayfrench during the Fall '11 term at University of Toronto- Toronto.
- Fall '11