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1.3 MEMBRANE STRUCTURE - Coggle Diagram
1.3 MEMBRANE STRUCTURE
1.3 U1 Phospholipids form bilayers in water due to the amphipathic properties of
phospholipid molecules
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Structure of phospholipids: -A polar organic molecule (e.g.choline, serine)
-A phosphate group
-A glycerol molecule
-2 fatty acid tails
Phospholipids arrange in a bilayer → Hydrophobic tail region face inwards & 2 hydrophilic head regions face the cytosolic and the extracellular fluids.
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Viscous membrane = Saturated hydrocarbon tails
Fluid membrane = Unsaturated hydrocarbon tails with kinks
1.3 U2 Membrane proteins are diverse in terms of structure, position in the
membrane and function
Integral proteins = Transmembrane & permanently attached Peripheral proteins = Temporarily attached & associate with 1 surface of the membrane
Structure of membrane proteins → Non polar / hydrophobic amino acids associate w/ the lipid bilayer & Polar / hydrophilic amino acids are located internally and associate w/ the aqueous solutions
Tertiary structure of transmembrane proteins = single helices / helical bundles OR beta barrels (common in channel proteins)
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1.3 Application: Cholesterol in mammalian membranes reduces membrane
fluidity and permeability to some solutes
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Cholesterol interacts with the fatty acid tails of phospholipids to moderate the fluidity of the membrane
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1.3 S2 Analysis of evidence from electron microscopy that led to the proposal
of the Davson-Danielli model
Davson-Danielli model: When viewed under a transmission electron microscope, membranes showed a characteristic 'trilaminar’ appearance
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1.3 S3 Analysis of the falsification of the Davson-Danielli model that led to the
Singer-Nicolson model
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Falsification evidence
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Freeze fracturing was used to split open the membrane and revealed irregular rough surfaces within the membrane → Proteins could be transmembrane
Membrane proteins were discovered to be insoluble in water (indicating hydrophobic surfaces) and varied in size
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