L2 - secretory Flashcards
Why do we need membrane traffiking?
- compartmentalisation ( complexity/specialisation)
- Enzymes can modify proteins in certain environments
- sequential modifications - proteins need to be exposed to distinct subsets of enzymes in different compartments
- retrieval of proteins/enzymes back to resident compartments
- targets proteins to correct compartments.
What is the order of compartments in the biosynthetic (secretory) pathway?
ER - cis golgi - trans golgi - PM/endosome
What is the order of compartments in the endocytic pathway?
cell surface - endosome - trans golgi - cis golgi - ER - lysosome
what is constitutive secretion?
Where a component is secreted continuously regardless of external factors/signals. ( no specific signal is required for secretion)
what is regulated secretion?
where a component is held in compartments (granules) until a required signal is received for secretion to occur. (e.g. Ach in NMJ)
where are endosomes derived from?
golgi membrane
what does ERGIC stand for?
endoplasmic reticulum - golgi intermediate compartment.
what is glycosylation?
A controlled enzymatic modification of a molecule (commonly proteins) by the addition of a sugar molecule
what did studies in the 1970s show us about biochemical compartmentalisation?
Gave us a good idea of compartmentalisaiton within the secretory pathway e.g. looked a insulin
- events associated with packaging/sorting/transport/ final exocytosis obscure
where are proteins modified by oligosachharide addition?
In the ER , but are then processed/trimmed in the golgi (+ other sugar transferases added in golgi)
what type of gycosylation can occur on proteins?
N- and O- linked glycosylation
what is the purpose of glycosylation?
- constrain and assist correct folding of protein
- help with recognition (act as a ligand) (can distinguish between cell types), processing into correct compartment, interact with ECM and sugars on other cells
- create variation to same protein
what type of sugars are the basis of the ABO blood type system?
O- linked sugars
Give examples of the importance of gylcosylation
- O-linked sugars basis of ABO blood typing
- muscular dystrophies caused by absence of certain sugars on the protein dystroglycan
- staphylococcus aureus toxin binds to specific sialic acid residues on certain human cell surface glycosylated proteins.
what can staphylococcus aureus cause?
can cause a range of illnesses, e.g. skin conditions, pimples, to meningitis and pneumonia, sepsis, TSS
