Vesicular Transport

• Vesicle


  A sphere-like structure pinched off from the cell membrane, with a phospholipid bilayer shell and contents inside
• Vesicle


  • Maintains the integrity of the phospholipid bilayer
  • Can transport contents to other locations
• Types of vesicular transport


  • Endocytosis
  • Exocytosis
• Endocytosis


  1. Formation of pit in membrane

  2. Clathrin coating on cytoplasmic side

  3. Vesicle pinches off
• Pinocytosis


  Cell "drinking" - taking in water and small solutes
• Phagocytosis


  Capturing and destroying bacteria and cell debris
• Receptor-mediated endocytosis


  Bringing in specific large molecules (macromolecules) using receptors
• Endocytosis followed by exocytosis is called transcytosis
• Exocytosis


  1. Vesicle fuses with cell membrane

  2. V-SNARE and T-SNARE proteins align and twist

  3. Membrane fusion occurs

  4. Contents released outside cell
• Vesicular trafficking


  Transport of contents within the cell, not just in/out
• Understanding membrane transport concepts is critical for understanding physiology and how cells function