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Membrane Structure

Membrane Structure. ● The plasma membrane separates the living cell from its nonliving surroundings. Proteins. Outside of cell. Outside of cell. Hydrophilic region of protein. Hydrophilic head. Hydrophobic tail. Hydrophilic head. Phospholipid bilayer. Hydrophobic tail.

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Membrane Structure

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  1. Membrane Structure ● The plasma membrane separates the living cell from its nonliving surroundings. Proteins Outside of cell Outside of cell Hydrophilic region of protein Hydrophilic head Hydrophobic tail Hydrophilic head Phospholipid bilayer Hydrophobic tail Phospholipid Cytoplasm (inside of cell) (a) Phospholipid bilayer of membrane Hydrophobic regions of protein Cytoplasm (inside of cell) (b) Fluid mosaic model of membrane

  2. Membrane Structure

  3. Membrane Structure ● Phospholipid structure Phospholipids are amphipathic molecules

  4. Membrane Structure

  5. Membrane Structure Membrane Models: Today 1935 *Membranes are fluid

  6. Membrane Structure Membranes are fluid

  7. Membrane Structure ● Some functions of membrane proteins Cytoplasm Fibers of extracellular matrix c Enzymatic activity b Cell signaling a Attachment to cytoskeleton and extracellular matrix e Intercellular joining f Cell-cell recognition d Transport Cytoplasm Cytoskeleton ● Cell surface – Extracellular Matrix

  8. Membrane Structure

  9. Membrane Transport

  10. Molecules of dye Membrane Net diffusion Net diffusion Equilibrium (a) Passive transport of one type of molecule Membrane Transport • Diffusion – a process in which molecules move from an area of high concentration to an area of low concentration

  11. Membrane Transport Animal cell H2O H2O H2O H2O Normal Lysing Shriveled Plasma membrane Plant cell H2O H2O H2O H2O Flaccid (wilts) Turgid Shriveled (a) Isotonic solution (b) Hypotonic solution (c) Hypertonic solution

  12. Membrane Transport Facilitated diffusion

  13. Membrane Transport • Active transport requires energy to move molecules across a membrane. Lower solute concentration Solute ATP Higher solute concentration

  14. Membrane Transport *Active transport Example: sodium-potassium pump

  15. Membrane Transport *Voltage *Membrane potential *Some ion pumps generate voltage across membranes Electrogenic pump:

  16. Membrane Transport *Each cell membrane has characteristic set of carrier proteins

  17. MEMBRANE TRANSPORT Passive Transport (requires no energy) Active Transport (requires energy) Diffusion Facilitated diffusion Osmosis Higher solute concentration Higher water concentration (lower solute concentration) Higher solute concentration Solute Solute Solute Water Solute ATP Lower water concentration (higher solute concentration) Lower solute concentration Lower solute concentration

  18. Traffic of Large Molecules • Exocytosis is the secretion of large molecules within vesicles. Outside of cell Plasma membrane Cytoplasm

  19. Traffic of Large Molecules • Endocytosis takes material into a cell within vesicles that bud inward from the plasma membrane.

  20. Transport of large molecules Exocytosis Types of endocytosis found in animal cells: Endocytosis *Phagocytosis *Pinocytosis *Receptor-mediated endocytosis

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