Flashcards in Week 2 Vesicular Transport Module Deck (48)
what are three functions of vesicular transport?
deliver newly made molecules to their final destinations, communicate with the extracellular environment, ingest extracellular particles and solutes.
What are the two major pathways of vesicular transport
secretory pathway and the endocytic pathway
what is the function of the secretory pathway
delivers newly made molecules to their proper position outside the cell
what is the function of the endocytic pathway
delivers extracellular components to the inside of the cell
where does secretory vesicular transport begin?
In general vesicles ____ off the _______ and fuse to the _______ while carrying _____
bud, donor compartment, target compartment, cargo
describe the role of protein coating in vesicle budding. what two functions does the coat play?
vesicles require a protein coat for budding. the protein coat helps pinch vesicle off donor membrane and helps sort sort the cargo
what are the three major protein coating proteins?
clathrin, COPI and COPII
Describe the structure of clathrin. how does this relate to function?
3 heavy chains and 3 light chains form a triskelion which forces vesicle into rounded shape.
How does clathrin bind the membrane of budding vesicles? (what is the binding cascade?)
Clathrin binds adaptin, adaptin binds cargo receptor, cargo receptor binds cargo
What is the role of dynamin in vesicle formation?
pinches off vesicle
what accounts for the variation in cargo carried by vesicles?
different adaptin molecules bind different cargo receptors in different regions of the cell.
What happens to the clathrin coat prior to the vesicle reaching the target compartment?
clathrin and adaptin are released from the vesicle and recycled
how does the vesicle find its way to the target compartment?
it moves along cytoskeletal elements within the cytoplasm
which proteins are responsible for docking and recognition of vesicles to target compartments?
Rab located on the vesicle binds the tethering protein located on the target membrane
which proteins are largely responsible for the fusion of the vesicle with the target membrane?
v-snare on the vesicle and t-snare on the target compartment
What types (3) of modifications or proteins occur in the ER?
Cys-Cys Disulfide bonds (interchain and intrachain)
lipid membrane anchors (addition of lipids that covalently anchor protein to the membrane
The initial glycosylation of proteins occurs in the ER
Oligosaccharides are generally added to which residues on a polypeptide chain?
what is the difference between N-lonked and O-linked glycoproteins?
N-linked: oligasaccharide added to Asn residue
O-linked: added to Ser or Threonine
what is the role of dolichol?
dolichol is a special membrane lipid in the ER that transfers its oligasaccharide group to the newly translated polypeptide
Describe the selectivity of exit from the ER
protein exit from the ER is highly selective. The ER uses chaperone proteins to ensure proteins fold correctly. If a protein cant be made to fold correctly it is degrade in cytosol
what is the difference between cis-golgi network and trans-golgi network?
Cis: where vesicles enter the golgi
Trans: where vesicles exit the golgi
Vesicles that exit the golgi are destined to go where?
endosome or plasma membrane
as a vesicle moves through the golgi what happens to its contents?
further sorting and modification of sugars and proteins
What are the two pathways of exocytosis
constitutive secretion, regulated secretion
describe constitutive secretion. what cells do this? role?
constantly occuring and seen in all cells. supplies PM with new proteins and lipids and releases things to extracellular space
describe regulated secretion. what cells do this? role?
release of vesicle contents to extracellular space in response to specific stimulus (receptor activation). only seen ins specialized secretory cells such as endocrine cells
what is the pathway of an ER protein from the ER to lysosome?
ER-->cis golgi-->trans golgi-->endosome-->lysosome
what is the role of lysosome? what type of enzymes to they house?
sites of molecular degradation. House acid hydrolases (nucleases, proteases, lipases)