The Secretory pathway Flashcards
What is the secretory pathway?
Pathway from the ER to the cell surface & endosomal pathway
What does the enzyme scramblase do?
Equilibrates lipids - scramblase catalyses flipping of phospholipid molecules
What does the energy-dependent ‘flippase’ do?
Ensure membrane asymmetry is maintained
What enzyme is used to transfer phosphatidylserine from the extracellular leaflet to the intracellular (cytotoxic) leaflet?
ATP-dependent translocase (flippase)
What enzyme is used to transfer phosphatidylserine from the intracellular (cytotoxic) leaflet to the extracellular leaflet?
Scramblase
What is the ER (endoplasmic reticulum) connected to?
Nuclear envelope
What is the ER (endoplasmic reticulum) made up of?
ER forms hollow tubes & flattened sacs. The chambers are cisternae.
What are the 2 types of ER (endoplasmic reticulum)?
- Rough ER (RER) outer membrane covered in ribosomes
- Smooth (SER) no ribosomes
What are the 4 functions of the endoplasmic reticulum?
- Quality control
- Synthesis
- Storage
- Detoxification
What molecules help newly synthesised linear sequences of amino acids to fold into tertiary & quaternary structures?
Chaperone proteins
What is the smooth endoplasmic reticulum (SER) responsible for?
- phospholipid & cholesterol synthesis
- steroid hormone production
- synthesis & storage of glycerides
- synthesis & storage of glycogen
- important role as a calcium store
What cells are responsible for Calcium signalling?
Acinar cells
Describe the process of vesicular transport between the ER & Golgi apparatus
- vesicles bud off ER
- vesicle fuses to the Golgi
What is the purpose of the coating of vesicles?
aids the formation of vesicles, however has to be discarded before vesicular fusion with the target compartment
What are the 3 types of coating of vesicles?
- clathrin
- COPI
- COPII
What is the function of SNAREs?
To aid vesicles reach the correct target
What are the 2 types of SNAREs involved in vesicular transport?
v-SNAREs - vesicular SNAREs (found in the vesicle membrane)
t-SNAREs - target SNAREs (found in the membrane of the target membrane)
What is the Golgi apparatus composed of?
flattened discs - cisternae (usually 5-6)
What are the 3 primary functions of the Golgi apparatus?
- modification & packing of secreted proteins
- renewal & modification of the plasma membrane
- delivery of material to other organelles, especially the endocytic pathway
What pathway transports plasma membrane & secreted proteins to the cell surface?
Constitutive secretory pathway in non-polarised cells
What network is considered a major sorting station for newly-made proteins?
Trans-Golgi Network
