5. The protein Secretory Pathway

• Protein secretory pathway


  The main organelles involved are: Ribosomes, Rough endoplasmic reticulum, Golgi body/apparatus, Transport and secretory vesicles
• Protein secretion


  1. Proteins are synthesised at the ribosome by translation

  2. Proteins that are going to be secreted are usually synthesised at ribosomes that are attached to the rough endoplasmic reticulum

  3. RER then folds the protein

  4. Protein leaves the RER in a transport vesicle

  5. Vesicle fuses with the golgi body/apparatus and releases the protein into the lumen of golgi body

  6. At the golgi body the protein can be modified, folded and then packaged into secretory vesicles

  7. Secretory vesicles bud off the golgi apparatus and travel through the cytoplasm to the plasma membrane

  8. Protein then leaves the cell via exocytosis
• Exocytosis


  • Moves large substances such as proteins to the outside of the cell (secretion)
  • Active process that requires energy
  • A vesicle will fuse with the plasma membrane and its contents will be released into the extracellular fluid