vesicles transport

Question 1

what determines the final location of proteins that end up in the prominent organelles in the cell? who is the exception to this?

Answer 1

proteins that end up in the mitochondria, peroxisomes, and nucleus do so by post translational means. they are made on free ribosomes and the transfer is mediated by the presence of organelle specific amino acid signal sequence. the exception are proteins destined for the ER they do not use this pathway

Question 2

what are the steps of nuclear transport?

Answer 2

1. cargo has nuclear recognition signal that is recognized by importin and binds to it.
2. the complex then travel into the nucleous/ organelle.
3. they are bound by Ran-GTP
4. binding of Ran-GTP causes the cargo to dissoicate from the importing but Ran-GTP remains bound to importin.
5. Ran-GTP bound to importin is tranported back out into the cytoplasm.
6. they are bound by GAP which hydrolyzes GTP on Ran to GDP causes the Ran-importin complex to dissociate.
   https: //www.youtube.com/watch?v=Q7F2vGwfsL8https://www.youtube.com/watch?v=Q7F2vGwfsL8
   https: //www.youtube.com/watch?v=Q7F2vGwfsL8

Question 3

which tranport pathway is mutated in Zellweger syndrom?

Answer 3

organelle localazation pathway of protein transport to the peroxisome.

Question 4

what causes the actual disease in Zellweger syndrome?

Answer 4

ZS is not caused by a defective pathway but rather a mutation in the amino acid sequence. the recogntion sequence on the amino acid is mutated and thus cannot be recognized by importin and is never transported to the nucelus. the synthesized proteins with no ability to get in the peroxisome remain in the cytoplasm until they are degraded

Question 5

contrary to popular belief, secretory protein synthesis begins in the

Answer 5

cytoplasm

Question 6

unlike intracellular proteins, secretory proteins are transported

Answer 6

cotranslationally

Question 7

when a secretory protein emerges from the cytoplasmic ribosome who is the first molecule to bind said protein and how does it do this?

Answer 7

when a secretory protein first emerges from the ribosome, it binds SRP (signal recognition peptide) which recognizes the signal peptide sequence on the N-terminus of the protein

Question 8

what are the steps to cotranslational protein transport

Answer 8

remember the signal peptide is actually removed after the protein has been localized in theb ER lumen

Question 9

why dont you ever find glycosilated proteins on the cytoplasm?

Answer 9

because glycosylation happens on the ER lumen

Question 10

what is the path of a secretory protein?

Answer 10

ribosomes–>ER–>Golgi–> membrane

Question 11

what is usually the sugar content of the glycosylation step?

Answer 11

cotranslational proteins are glycosylated with a 9 manos oligosachiride

Question 12

what are the steps to COP-II vessicle assembly?

Answer 12

1. inactive Sar-1 bound to GDP is phosphorylated by GEF to produce active Sar-1-GTP.
2. Sar-1-GTP inserts into the ER membrane and exposes its binding site
3. COP binds to Sar-1
4. recruitment of other CCOP II subunits allows it to select which protein in the ER to find and transport.

Question 13

where do the different protein coats transfer to?

Answer 13

COP II: ER-Golgi

COP I: retrograde (brings shit back to be reprocessed

Clatherine: cell surface to early endosome

TGN to late endosome

late endosome to TGN

Question 14

even though each vesicle has its own Rab (Rab is on the cargo), what adds more specificity to vesicle transport

Answer 14

V-snares on the vesicle can onlyh bind to aparticular t-snare on the target/ membrane

Question 15

what is a KDEL sequence?

Answer 15

process by which a miss routed protein is retrieved and brough back to the TGN for sorting

Question 16

where does sorting of proteins to be tranfered to the lysosomes, cell membrane happen?

Answer 16

in the trans golgi netowork

Question 17

if a protien is marked by the manose-6-phosphate residue where is it being transported?

Answer 17

lysosome

Question 18

what are the steps to endocytosis?

Answer 18

1. cargo binds to the receptors on the cell surface
2. then clatherine binds to the lumen side of the receptors
3. then the vesicle is formed and transported into the cell into the early endosome.
4. in the early endosome, the vesicle is dissociated and the cargo broken down.
5. from here the vesicles can either be returned to the cell surface or be sent to the lysosome to be degraded

Question 19

why would there be a need to send the vesicles to be degraded?

Answer 19

it is a way of down regulation because the less vesicles yiu have on the surfface the less cargo would be transported into the cell

Question 20

what causes hypercholestrolnemia?

Answer 20

defect in the coated pit binding site of the cell surface receptors

Question 21

enveloped viruses (if you have the time)

Answer 21

a