BE230_Lecture_2 - BE230 Lecture 2 Chemical composition of...

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Unformatted text preview: BE230 Lecture 2 Chemical composition of membranes Dr Rosaleen Devery School of Biotechnology At end of this lecture You will be able to describe 1. Lipid composition of membranes-chemical structures of Pls, SLs, C 2. Compare lipid composition of RBC, myelin, mitochondria, E.coli 3. Structure & Function of liposomes 4. Types of linkages that join sugars to proteins 5. Which oligosaccharides produce A,B,O blood types 6. Structure and function of 3 classes of membrane proteins 7. Effect of temperature on lipid bilayer 8. What enzymes desaturate fatty acidshow affect membrane fluidity 9. How PLs are distributed in plasma membrane of RBC 10. 3 possible movements of phospholipids in membrane 11. Experiment that showed membrane proteins are mobile 12. A technique called FRAP that measures diffusion rates of membrane proteins 13. Different functions of plasma membrane of an intestinal epithelial cell 7 Membrane functions 1. Compartmentalisation 2. Scaffold for biochemical activities 3. Provide a selectively permeable barrier 4. Transporting solutes 5. Respond to external signals 6. Intercellular interaction 7. Energy transduction 3 types of membrane lipids Phosphoglycerides (PLs) Sphingolipids Cholesterol Phosphoglycerides Diglycerides 2 of the hydroxyl groups of glycerol are esterified to fatty acids The third is esterified to a hydrophilic phosphate group Groups attached to phosphate include Choline Ethanolamine Serine Inositol Small, hydrophilic, water soluble domain= head group PS & PI are ve charge PC, PE are neutral Fatty acyl chains are hydrophobic, unbranched, C16-C20 SFA, MUFAor PUFA Phoshoglycerides have Amphipathic character Sphingolipids sphingosine linked to a fatty acid by amino group ie ceramide Additional groups are esterified to terminal alcohol of sphingosine Eg If PC is added, it is sphingomyelin If a carbohydrate is substituted, it is glycolipid Eg cerebroside, ganglioside Also called amphipathic lipids Cholesterol 50% of lipid molecules in plasma membrane Absent from plant and bacteria Smaller than other lipids Less amphipathic Their small hydrophilic hydroxyl group is oriented towards membrane surface Remainder of molecule is embedded in lipid bilayer Membrane Protein/lipid (wt/wt) Cholesterol /polar lipid Major polar lipids Myelin 0.25 0.7-1.2 Cer,PE,PC Liver pm 1.0-1.4 0.3-0.5 PC,PE,PS, SM Intestinal villi 4.6 0.5-1.2 As above RBC ghost 1.5-4 0.9-1 SM,PE,PC, PS ER 0.7-1.2 0.03-0.08 PC,PE,SM Outer mitochond 1.2 0.03-0.09 Inner 3.6 0.02-0.04 Lipid bilayers Ability to self assemble...
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This note was uploaded on 01/05/2010 for the course FSH BT taught by Professor Ianmarison during the Fall '09 term at Dublin City University.

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BE230_Lecture_2 - BE230 Lecture 2 Chemical composition of...

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