Membrane Junctions

  1. Location of:
    Tight junctions
    • at the very apical ends of hte junctional complex between adjacent epithelial cells 
    • run parallel to each other and to the apical surface
  2. Location of:
    gap junctions
    • tightliy linked to one another through noncovalent interactions
    • come cllose but don't touch
  3. Location of: 
    cytoplasmic channels that pass through cell walls of adjacent cells
  4. Function of 
    tight junctions
    • serve as barrier and fences that help maintian the polarized character of epithelial cells
    • contact at intermittent points
    • involved in signaling
    • impermeable to H2O
    • blood brain barrier
  5. Function of 
    gap junctions
    • intercellular communition
    • communication between the cytoplasm of adjacent cells
    • stimulates cardiac and smooth muscle
    • can put cells into intimate cytoplasmic contact
  6. Function of 
    • connect cytoplasm of two adjacent plants
    • capable of dilation due to movement proteins
  7. Structure of 
    tight junctions
    • integral proteins of tight junctions form continuous fibrils that encircle the cell
    • not all have same permeability
  8. Structure of 
    gap junctions
    made of connexins, which form connexons, which become tightly linked to one another through noncovalent interactions
  9. Structure of plasmodesmata
    lined by plasma membrane and have a dense central structure (desmotubule) made from the SER of both cells
Card Set
Membrane Junctions