ER Flashcards
What do vesicle receptor proteins regulate?
Intracellular trafficking of the vesicle to the proper recipient membrane.
Explain the biosynthetic pathway.
Materials are transported from the ER, to the Golgi, to the endosomes, and finally to either lysosomes or the PM
How are constitutive secretion and regulated secretion different?
They both transport materials from the ER to the Golgi, but constitutive uses secretory vesicles to transport to the PM while regulated uses secretory granules.
What is the name of the trafficking pathway that takes materials into the cell?
The Endocytic Pathway
What are the main functions of the ER?
Protein and lipid synthesis, protein folding, and processing.
What is the organelle with the largest surface area in the cell?
The ER
ER tubule and cisternae shapes are mediated by what type of protein?
Reticulons
What can be found in the aqueous space inside the ER tubules and cisternae?
The ER lumen
What is the function of the ER Exit Sites?
They are regions where transport vesicles bud off on route to the Golgi.
True or False: the outer nuclear membrane is continuous with the RER
True
What type of receptor acts as a docking site for SRPs at the RER lumen?
SRP receptors
Where do ribosomes bind to translate proteins into the RER?
Translocon
What does signal peptidase do?
It cleaves signal sequences entering in the RER lumen translocon
What is the function of reticuloplasmins?
They are chaperones that operate in the ER and fold proteins.
In the process of inserting IMPS into the RER, what is the function of TMD?
It serves as a stop-transfer sequence
What is needed in order to open translocons in the RER?
Either TMD or a signal sequence
Which two types of membrane proteins/lipids are NOT synthesized at the ER?
Glycolipids, and unique mitochondrial and chloroplast proteins/lipids.
True or False: nascent ER membrane proteins are orientated in a symmetrical manner in the lipid bilayer
False. They are asymmetrically distributed
What is the purpose of glycosylation in processing nascent proteins?
It adds side chains to the amino acids in order for proper folding and binding to occur.
Name the most common type of protein glycosylation.
N-linked glycosylation, where sugar monomers are added to the terminal amino group of a asparagine (N).
What are the two stages of N-linked glycosylation?
Core glycosylation and core modification
What is the function of ER membrane-bound glycosyltransferases?
They synthesize the core oligosaccharide in the process of glycosylation, and link it to a N residue.
What is the purpose of core modification in the process of glycosylation?
It is to trim and modify the core oligosaccharide, and properly fold it.
What happens to misfolded proteins after glycosylation?
They are recognized by GT monitoring enzymes and recycled until properly folded, or destroyed.
