Endomembrane System Part 2 Flashcards
What does the endomembrane system do?
Materials move within the endomembrane system via the biosynthetic, secretory, and endocytic pathways via transport vesicles
What is the Endoplasmic Reticulum?
ER is the starting point for both the secretory and biosynthetic pathway
It is the site of protein synthesis, protein folding, and processing
What is the structure of the Endoplasmic Reticulum?
A highly complex network of membrane-enclosed, rod-like tubules and sheet-like cisternae (flattened sacs)
It is the organelle with the largest surface area
What is the lumen of the Endoplasmic Reticulum?
Aqueous space inside of ER tubules and cisternae
What are the tubules and cisternae in the Endoplasmic Reticulum?
They are shapes that are mediated by reticulons
What are reticulons?
Unique ER integral membrane proteins that possess a ‘hairpin’ (V-shaped) secondary structure and regulate ER membrane curvature (‘bending’) and overall shape of the ER
Why is the Endoplasmic Reticulum special?
It is a highly dynamic network
What do the ER tubules and cisternae do?
They are in constant flux
They undergo constant bending, fusion, fission
What does the ER consist of?
Distinct regions of the ER network that possess unique morphologies and/or functions
RER and SER are two classic examples of ER subdomains
What is the RER?
Mostly cisternae with bound ribosomes, involved in protein and membrane phospholipid synthesis
What is the SER?
Mostly curved tubules lacking ribosomes, involved in calcium storage and hormone synthesis –> it is not involved with proteins
What does each ER subdomain possess?
Each possesses a unique complement of proteins and membrane lipids that mediate its distinct function(s)
What is the nuclear envelope?
It is an ER subdomain
The outer nuclear membrane is continuous with RER, contains Nups, and attached ribosomes
What is the Mitochondria and Plasma Membrane-Associated Membranes (MAM & PAM)?
It is an ER subdomain
Regions of ER that make direct contact with mitochondria or the pm, respectively; involved in membrane protein and lipid exchange
What is the ER Exit Sites (ERES)?
It is an ER subdomain
Regions where transport vesicles bud off from the ER en route to the Golgi