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Outline Lecture 5 - Membrane and Transport - Chapter 5 Instructor outline(1).docx

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1Module 2: Lesson 4Membrane and Transport – Chapter 5I.Functions of the Plasma MembraneA.Cell-to-cell recognition& Cell AdhesionB.Signal transduction(cell signaling)C.Attachment to the cytoskeletonD. Adhesionto the ECME. TransportII.Membrane StructureA.Fluid-Mosaic Model1. Proteins (mosaicpart)a. Integral proteins1.)Transmembrane proteins2.)Lipid anchored proteinsb. Peripheral proteins2. Phospholipids – (fluidpart)B.Fluidity vs Viscosity - bilayer semi-fluidityis essential for normal cell function, growth,and development1. Leaflet bilayer – asymmetric: certain lipids may be more abundant in one leafletcompared to the other.a. Cytosolic leafletb. Extracellular leaflet2. Selectivepermeability – allowing the passage of some ions and molecules but notothersa. Essential molecules – (glucose / amino acids) enter the cellb. Waste products – exit the cellIII.Fluidity of the MembraneA.Phospholipid movement1. Rotationally – energetically favorable2. Laterally – (exchanges places with its neighbor) energetically favorable, occurs 107timer per second (37°C)3. Flip-flop – (movement from one leaflet to the opposite leaflet) energeticallyunfavorable, therefore it requires ATP and the catalyticactivity of the enzyme FlippaseB.Chemical Properties of Phospholipids that Affect Fluidity1. Amphipathica. Polar head group – charged region / hydrophilicb. Non-polar tail – uncharged region / hydrophobic2. Length of fatty acyl tailsa. Shorter tails – (18 – 20 Carbons are most common) morefluid, less likely to interactwith each otherb. Longer tails – lessfluid (more viscous)1.)Lipid rafts – regions of long and tightly packed tails; move through themembrane as a single unit; associated with cholesterol3. Double bonds
2a. Phospholipid is unsaturated

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Term
Fall
Professor
Chitra Sundaram
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