Secretion Flashcards
Secretion definition
Release of useful molecules from a cell
Audio radiography of pancreatic cells
- Inject radioactive AAs into rat
- Remove pancreas/cells after known time and prep for e- microscopy (thin section)
- Mount sections on supports & coat with photographic emulsion
- Dark room for known amount of time (allow for decay and exposure of emulsion)
- Develop and fix with photographic chemicals (ID proteins)
Secretory pathway
RER => transport vesicles => Golgi apparatus => secretory vesicles => exocytosis
Early stage of translation
Transcription, mRNA exits thru nuclear pore
Ribosome joins on at start codon/signal sequence and translation begins
Signal peptide created binds to receptor on ER and strand released into ER, where it cont. translation
SER functions
Lipid synthesis and metabolism, detox reactions
RER function
Entry of proteins into ER, insertion of membrane proteins into lipid bilayer, simple glycosilation reactions, correct protein folding
Golgi function
- receives vesicle traffic from ER (proteins etc)
- identify faulty proteins (quality control)
- complex glycosilation rx (addition of sugars)
- sorting and packaging of contents
- targeting of products to final destinations
Pathways of secretion from Golgi
- Regulated pathway
- Lysosomal
- Constitutive
Regulated pathway from Golgi
Mannose-6-phosphate receptor, stored in cell until needed, only when external signal given
Receptor-dependent transport
Lysosomal pathway from Golgi
No receptor, sends vesicles to lysosomes
Constitutive pathway from golgi
Secretory product receptor, to secretory granule, secretes constantly
Secretory vesicle functions
Controls concentration of contents
Targeting and transport of cell surface/lysosome
Membrane fusion and release of product
Delivery of new membrane lipids and protein cell surface
Exocytosis
Fuses vesicle membrane with CM
Expands membrane, but balances with endocytosis (which takes)
