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Membrane structure and function

Membrane structure and function. Membranes are made of fat (lipids). Phospholipids. Hydrophilic head. Hydrophobic tails. WATER. Hydrophilic head. Hydrophobic tail. WATER. Bilayer. Bilayer. Biological membranes are fluid mosaics of lipids and proteins. Hydrophilic region

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Membrane structure and function

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  1. Membrane structure and function

  2. Membranes are made of fat (lipids) Phospholipids

  3. Hydrophilic head Hydrophobic tails

  4. WATER Hydrophilic head Hydrophobic tail WATER Bilayer

  5. Bilayer

  6. Biological membranes are fluid mosaics of lipids and proteins

  7. Hydrophilic region of protein Phospholipid bilayer Hydrophobic region of protein Fluid Mosaic Model of Singer and Nicolson (1972)

  8. Evidence for fluid mosaic model Freeze fracture (electron microscopy)

  9. Extracellular layer Proteins Knife Plasma membrane Cytoplasmic layer Extracellular layer Cytoplasmic layer

  10. Lateral movement (~107 times per second) Flip-flop (~ once per month) Movement of phospholipids Membrane fluidity

  11. Viscous Fluid Saturated hydro- carbon tails Unsaturated hydrocarbon tails with kinks Membrane fluidity

  12. Cholesterol Cholesterol within the animal cell membrane

  13. Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Cholesterol Peripheral proteins Microfilaments of cytoskeleton Integral protein CYTOPLASMIC SIDE OF MEMBRANE Membrane Proteins

  14. Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Cholesterol Peripheral proteins Microfilaments of cytoskeleton Integral protein CYTOPLASMIC SIDE OF MEMBRANE Membrane Proteins

  15. EXTRACELLULAR SIDE N-terminus C-terminus CYTOPLASMIC SIDE a Helix Transmembrane protein

  16. Membrane Proteins: functions Signal Enzymes Receptor ATP Enzymatic activity Transport Signal transduction

  17. Membrane Proteins: functions Glyco- protein Attachment to the cytoskeleton and extra- cellular matrix (ECM) Cell-cell recognition Intercellular joining

  18. Moving stuff around • Passive transport • Active transport • Bulk transport

  19. Diffusion

  20. Molecules of dye Membrane (cross section) WATER Net diffusion Net diffusion Equilibrium Diffusion of one solute Passive Transport

  21. Passive Transport • Passive transport is the diffusion of a substance across a biological membrane • No energy required

  22. Lower concentration of solute (sugar) Higher concentration of sugar Same concentration of sugar H2O Selectively permeable mem- brane: sugar mole- cules cannot pass through pores, but water molecules can Osmosis Osmosis Diffusion of water across a membrane

  23. Isotonic solution Hypertonic solution Hypotonic solution Animal cell H2O H2O H2O H2O Shriveled Normal Lysed

  24. Getting across the membrane

  25. Rather directly

  26. Exocytosis

  27. Some material can diffuse through membranes on their own Diffusion Passive

  28. Some materials diffuse through only with help Diffusion Passive

  29. Some materials must be pumped through membranes Against Diffusion Active (not passive)

  30. Passive transport Active transport ATP Facilitated diffusion Diffusion

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