Cell Membrane

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Cell Membrane

• Haixu Tang
• School of Informatics

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Membrane Lipids Are Amphipathic Molecules
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hydrophilic and hydrophobic molecules interact
differently with water
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Packing arrangements of lipid molecules
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The spontaneous closure of a phospholipid bilayer
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Phospholipid mobility
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The other composition of membraneCholesterol and
glycolipids
It inhibits possible phase transitions (1)
decreases the permeability of the bilayer to
small water-soluble molecules (2) prevents the
hydrocarbon chains from coming together and
crystallizing.
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Cholesterol
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Glycolipid
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Four major phospholipids in mammalian plasma
membranes
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Cell wall
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Lipid raft
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The asymmetrical distribution of phospholipids
and glycolipids
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Functions of phospholipids in cell signaling
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Membrane proteins
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Membrane attachment of Water soluble proteins
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Transmembrane polypeptide chain crossing the
lipid bilayer
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Using hydropathy plots to localize potential
a-helical membrane-spanning segments
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b-barrels (occasionally)
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Solubilizing membrane proteins with a mild
detergent
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Two detergent
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Reconstituting functional membrane protein system
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Red cell membrane
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Preparing red cell ghosts
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SDS polyacrylamide-gel electrophoresis pattern of
the proteins in the human red blood cell membrane
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Three major ways of proteins association with
membranes

• Noncovalently Associated with the Cytosolic Side
  Spectrin
• Extends Through the Red Blood Cell Lipid Bilayer
  as a Single a Helix Glycophorin
• Multipass Membrane Protein Band 3 protein

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Spectrin cytoskeleton protein
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Spectrin-based cytoskeleton
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Glycophorin single pass membrane proteins
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Band 3 Anion Transporter
The polypeptide chain (about 930 amino acids
long) is thought to extend across the bilayer 12
times.
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Photosynthetic reaction center
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The Cell Surface Is Coated with Sugar Residues
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Carrier proteins and channel proteins
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A typical ion channel
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The gating of ion channels
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Potassium ion gate
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Passive and active transport
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Three ways of driving active transport