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Membrane Structure and Function

Membrane Structure and Function. Membrane structure Traffic across the membranes. Membrane Structure. Fluid Mosaic Model Made of lipids, proteins and carbohydrates Mosaics of structure and function Cell-to-cell recognition and carbohydrates. Membrane Structure. Proteins, by position

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Membrane Structure and Function

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  1. Membrane Structure and Function Membrane structure Traffic across the membranes

  2. Membrane Structure • Fluid Mosaic Model • Made of lipids, proteins and carbohydrates • Mosaics of structure and function • Cell-to-cell recognition and carbohydrates

  3. Membrane Structure • Proteins, by position 1) peripheral 2) integral: unilateral and transmemberane • Lipids 1) phospholipids 2) cholesterol • Carbohydrates

  4. Protein Function • Transport • Enzymes • Receptor sites • Cell adhesion • Anchor for cytoskeleton • Cell-to-cell recognition • Anchor for ECM

  5. Lipid Function • Phospholipids –amphipathic, bilayer, major structural component, barrier • Cholesterol – modulate fluidity

  6. Carbohydrates • Cell-to-cell recognition • “Name tags” • Usually branched oligosaccharides • Sorting of embryonic cells • “Self” recognition

  7. Traffic Across the Membranes • Membrane is selectively permeable • Passive transport • Active transport • Concentration gradient • Energy source

  8. Passive Transport-I • Material moves down the gradient • Diffusion • Osmosis-water diffusion • Particles must be 1) small 2) nonpolar 3) uncharged

  9. Passive Transport-II • Group translocation • Facilitated diffusion • Requires transport protein • Still down the gradient • Used for: 1) charged particles 2) LARGE particles 3) polar molecules

  10. Osmosis • Water diffusion thru a membrane • Down the gradient • Hypertonic, isotonic, and hypotonic • Plasmolysis, turgor, crenation

  11. Active Transport • cellular energy • Against the gradient • Ion pumps • Exocytosis and Endocytosis • Phagocytosis and pinocytosis • Receptor mediated endocytosis

  12. Bulk Transport • Movement via vesicles • Exocytosis-out • Endocyctyosis-in

  13. Videos and Websites • http://www.sumanasinc.com/webcontent/animations/content/endocytosis.html • http://www.johnkyrk.com/diffusion.html • http://www.youtube.com/watch?v=K7yku3sa4Y8&NR=1

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