Bio 103 Chapter 5: 149164 Lecture 2 Chapter 7: 245260

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Bio 103 Chapter 5 149-164 Lecture 2
Chapter 7 245-260

• Membrane Structure and
• Membrane Transport I Pumps

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Membrane Structure and Transport-Overview

• Biomembranes lipid composition/structural
  organization
• Cell membranes consist of phospholipid bilayers
• Cell membranes consist of three classes of
  membrane lipids
• Biomembrane-associated proteins determine
  membrane activity
• Transport across cell membranes
• Few molecules cross membranes by passive
  diffusion
• Classes of membrane transport proteins
• ATP-powered pumps
• Ion channels
• Transporters (Uniporters, Symporters and
  Antiporters)
• ATP-powered pumps
• P-class pump Na/K ATPase
• ABC superfamily MDR-1

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Membrane Structure and Transport

• Biomembranes lipid composition/structural
  organization
• Cell membranes consist of phospholipid bilayers
• Cell membranes consist of three classes of
  membrane lipids
• Biomembrane-associated proteins determine
  membrane activity
• Human ABO blood groups
• Dialysis

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Three views of a cell membrane
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The parts of a phospholipid molecule
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5-5 Three classes of membrane lipids
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Four major phospholipids in mammalian plasma
membranes
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The structure of cholesterol
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Cholesterol in a lipid bilayer
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5-6 FRAP experiments can quantify lateral
movements of lipids and proteins within the
plasma membrane
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5-8 Effects of lipid composition on bilayer
thickness and curvature
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Lipid rafts small, specialized areas in
membranes where some lipids and proteins are
concentrated
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Model of lipid raft
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Sphingomyelin rafts (orange) and associated
proteins (yellow) within the plasma membrane
background (black)
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5-11 Proteins associated with lipid bilayer
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Solubilizing membrane proteins with a mild
detergent
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• The structures of two commonly used detergents
• Green hydrophobic portion
• Blue hydrophilic portion

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The use of mild detergents for solubilizing,
purifying and reconstituting functional membrane
systems
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Plasma membrane proteins are typically decorated
with carbohydrates (sugars)
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Human ABO blood-group antigens
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5-18 Effect of external ion concentration on
water flow across the plasma membrane
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Membrane Structure and Transport

• Biomembranes lipid composition/structural
  organization
• Transport across cell membranes
• Few molecules cross membranes by passive
  diffusion
• Classes of membrane transport proteins
• ATP-powered pumps
• Ion channels
• Transporters (Uniporters, Symporters and
  Antiporters)
• ATP-powered pumps
• P-class pump Na/K ATPase
• ABC superfamily MDR-1 (Drug resistance)

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7-1 Relative permeability of a pure phospholipid
bilayer
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7-2 Overview of membrane transport proteins
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The Na/K pump
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A model of the pumping cycle of the Na/K pump
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7-6 Another example of ATP powered transport
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7-11 Structural model of a bacterial ABC protein
similar to mammalian MDR-1
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7-12 Functional model of transport by MDR-1