Ap bio ch5membranes
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Ap bio ch5membranes Ap bio ch5membranes Presentation Transcript

  • Membrane Structure and Function Chapter 5
  • Outline
    • Membrane Models
      • Fluid-Mosaic
    • Plasma Membrane Structure and Function
      • Protein Functions
      • Plasma Membrane Permeability
        • Diffusion
        • Osmosis
        • Transport Via Carrier Proteins
    • Cell Surface Modifications
  • Membrane Models
    • Fluid-Mosaic Model
      • Membrane is a fluid phospholipid bilayer in which protein molecules are either partially or wholly embedded.
  • Fluid-Mosaic Model
  • Plasma Membrane Structure and Function
    • Plasma membrane separates internal environment from the external environment.
    • Hydrophilic polar heads face outside, and hydrophobic nonpolar tails face each other.
  • Plasma Membrane Structure and Function
    • Proteins may be peripheral or integral.
      • Peripheral proteins are found on the inner membrane surface.
      • Integral proteins are embedded in the membrane.
  • Protein Functions
    • Channel Proteins - Involved in passage of molecules through membrane.
    • Carrier Proteins - Combine with substance to aid in passage through membrane.
    • Cell Recognition Proteins - Help body recognize foreign substances.
  • Protein Functions
    • Receptor Proteins - Allow molecule binding, causing protein to change shape and bring about cellular change.
    • Enzymatic Proteins - Carry out metabolic reactions directly.
  • Plasma Membrane Permeability
    • Plasma membrane is differentially permeable.
      • Passive Transport - No ATP requirement.
        • Molecules follow concentration gradient.
      • Active Transport - Requires carrier protein and ATP.
  • Crossing Plasma Membrane
  • Diffusion
    • Diffusion - Movement of molecules from a higher to a lower concentration until equilibrium is reached.
      • Down concentration gradient
    • A solution contains a solute (solid) and a solvent (liquid).
  • Diffusion
  • Osmosis
    • Osmosis - Diffusion of water across a differentially (selectively) permeable membrane due to concentration differences.
      • Osmotic pressure is the pressure that develops due to osmosis.
        • The greater the osmotic pressure, the more likely water will diffuse in that direction.
  • Osmosis
  • Osmosis
    • Isotonic Solution - Solute and water concentrations both inside and outside the membrane are equal.
    • Hypotonic Solution - Solution with a lower concentration of solute than the solution on the other side of the membrane.
      • Cells placed in a hypotonic solution will swell.
        • Lysis
  • Osmosis
    • Hypertonic Solution - Solution with a higher concentration of solute than the solution on the other side of the membrane.
      • Cells placed in a hypertonic solution will shrink.
        • Plasmolysis
  • Transport by Carrier Proteins
    • Carrier proteins combine with a certain molecules which are then transported through the membrane.
      • Facilitated Transport
        • Small molecules follow concentration gradient by combining with carrier proteins.
  • Transport by Carrier Proteins
      • Active Transport
        • Small molecules move against their concentration gradient by combining with carrier proteins.
  • Membrane-Assisted Transport
    • Large marcomolecules are transported into or out of the cell by vesicle formation.
      • Exocytosis - Vesicles fuse with plasma membrane as secretion occurs.
  • Membrane-Assisted Transport
      • Endocytosis - Cells take in substances by vesicle formation.
        • Phagocytosis - Large, solid material.
        • Pinocytosis - Liquid or small, solid particles.
        • Receptor-Mediated - Specific form of pinocytosis using a coated pit.
  •  
  • Cell Surface Modifications
    • Cell Surfaces in Animals
      • Junctions Between Cells
        • Adhesion Junctions
          • Intercellular filaments between cells.
        • Tight Junctions
          • Form impermeable barriers.
        • Gap Junctions
          • Plasma membrane channels are joined (allows communication).
  • Cell Surface Modifications
      • Extracellular Matrix
        • Meshwork of polysaccharides and proteins in close association with the cell that produced them.
    • Plant Cell Walls
      • Plants have freely permeable cell wall, with cellulose as the main component.
        • Joined by plasmodesmata that spans cell wall and contains strands of cytoplasm that allow passage of material between cells.
  • Review
    • Membrane Models
      • Fluid-Mosaic
    • Plasma Membrane Structure and Function
      • Protein Functions
      • Plasma Membrane Permeability
        • Diffusion
        • Osmosis
        • Transport Via Carrier Proteins
    • Cell Surface Modifications
  •