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SL+D103+lecture+2+WEB - D103: Cell Biology Dr. Shin Lin...

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D103: Cell Biology Dr. Shin Lin
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Lecture 2 Biological Membranes I: Structural Components Recommended Reading: MBOC (5 th edition) 617-650
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 3 Model of Plasma Membrane Complex and Dynamic Structure with Multiple Components for Multiple Functions
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 4 KEY CONCEPTS Membranes separate cells and organelles Membranes consist of lipid bilayers and proteins Membranes are dynamic
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 5 Three sections in this lecture: I. Why do cells need membranes? II. Fluid mosaic model of membrane structure Membrane lipids: barrier function Membrane proteins: transport/communication function III. Lipid rafts
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 6 Why do cells need membranes?
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 7 Requirements for a Biological Membrane Permeability Barrier separates inside from outside Selectively Permeable allows exchange with the environment Flexible (fluid ) and “Smart” allows shape change and can communicate with the environment Growth, move m ent, change of shape
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 8 Membrane types : • External (plasma) membrane = cell membrane • Internal membranes = organelle membranes
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 9 I. Why do cells need membranes? II. Fluid mosaic model of membrane structure A. Membrane lipids: barrier function Membrane lipids are amphiphilic Lipids form bilayers in aqueous solutions Classes of membrane lipids: phosphoglycerides, sphingolipids, cholesterol B. Membrane proteins: transport/communication function III. Lipid rafts
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 10 History of Understanding Membrane Structure 1920s = cellular membranes consist of lipid bilayers 1940‟s = lipids alone insufficient to allow for full membrane function, hypothesized association of membrane proteins 1970‟s = Fluid Mosaic Model of membranes: membrane proteins float in a fluid, phospholipid bilayer 2000+ = membranes partitioned into rafts and non-raft phases
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 11 Fluid Mosaic Model of biological membranes: Lipids assemble into bilayers in which proteins form the active components of signal transduction and transport First described in 1972 by Singer and Nicolson Fixed Mosaic Artwork
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 12 Phospholipids are Amphiphilic” phospholipids differ in: - head group - degree of fatty acid tail saturation (# of double bonds) - length of fatty acid tails (amphi = both)
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D103 Fall 2011 Lecture 2 © Lin All rights reserved 13 Four Major Phospholipids in Mammalian Plasma Membranes Phosphoglycerides (PE, PS and PC) are derived from glycerol Sphingomyelin is derived from sphingosine All have phosphate-head group and two long chain fatty acid tails glycerol fatty acid ethanol amine
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SL+D103+lecture+2+WEB - D103: Cell Biology Dr. Shin Lin...

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