Cleavage of proinsulin to insulin occurs in the :
a) cytosol
b) RER
c) Golgi
d) Secretory vesicle
e) Lysosome
a) cytosol
b) RER
c) Golgi
d) Secretory vesicle
e) Lysosome
As does Costanzo. Cleavage occurs in the golgi immediately prior to packaging. Then both insulin and c peptide is secreted together.Robbins says it is Golgi
Robbins says it is Golgi
As does Costanzo. Cleavage occurs in the golgi immediately prior to packaging. Then both insulin and c peptide is secreted together.
So sources that say Golgi: UW, Robbins, lipincot biochem, costanzo physio, guyton physio
secretory vesicle:UW, Berne-levy physio, Marks biochem, Uptodate.com
Who do you trust?
If you know the mechanism of how protein synthesis and packaging works then there will be no confusion.
Proinsulin is packaged in the Golgi apparatus with protease and released together as a secretory vesicle. It cannot be other way around since Golgi IS the packaging center.
Once the appropriate signal is received, protease then splits the proinsulin into C peptide and the active insulin. The secretory vesicle fuses with the membrane and both are released.
Apples and Oranges.But why can't cleavage occur in the golgi vesicle before being released (like DA -> NE in neuronal vesicles)?
That's exactly the reason why they can't directly ask this on the test except to test the concept of protein synthesis and trafficking.Things like this make me wonder why this type of stuff is important to clinical medicine lol - if 3/4 specialized resources are conflicted on EXACTLY where, then why does it matter!?