L48 Protein Secretion Flashcards
What molecules remove introns and ligate the exons together to form mature mRNA?
Ribonucleoprotein complexes (spliceosomes)
What is added to 5’ end of mRNA, following transcription?
7-methylguanosine cap
What is added to 3’ end of mRNA, following transcription?
Poly(A) tail
What does ‘open reading frame (ORF)’ refer to?
The region between the start codon and the stop codon on mRNA.
How does the endoplasmic reticulum locate a growing protein chain?
Polypeptide chain activates signal-recognition particle. This binds to SRP receptor in ER membrane. The ribosome is bound to a translocation channel and passes the polypeptide chain straight through it into the lumen of the ER.
What are the 2 types of protein secretion?
1) Constitutive secretion: all cells secrete proteins required for general things (e.g. extracellular matrix proteins)
2) Regulated secretion: specialised secretory cells produce proteins that are stored in vesicles for release in response to signal (e.g. pancreatic acinar cells)
In which organelle are proteins folded into their correct 3D structure?
Endoplasmic reticulum
Which cells secrete glucagon in the pancreas?
Alpha-cells
Found in islets of Langerhans
Which cells secrete insulin in the pancreas?
Beta-cells
Found in islets of Langerhans
Which cells secrete somatostatin in the pancreas?
Delta-cells
Found in islets of Langerhans
What is unusual about secretion in pancreatic acinar cells?
Most of the proteins synthesised are secreted.
mainly digestive zymogens - trypsinogen and chymotrypsinogen
What determines where protein synthesis takes place?
mRNA - determines whether synthesis occurs in cytosol or RER.
Contains a signal sequence that activates signal recognition protein, leads to ribosome binding to translocon on ER membrane.
Where are transmembrane proteins synthesised?
RER
Where are lipids synthesised?
ER
Where are lumen proteins (e.g. lysosomes) secreted?
ER
