mod 4

Question 1

what are the components of the endomembrane system?

Answer 1

ER, golgi , endosomes and lysosomes (NOT perosixomes)

Question 2

Cotranslational import

Answer 2

peptide moves across the ER to remain or is transported by vesicles to endomembrane system (ribosome on ER)

Question 3

posttranslational import

Answer 3

peptides for cytosol or nucleus, mito, chloroplasts, or peroxisomes move via postranslational (free ribosomes)

Question 4

first 3 steps of the signal mechanism

Answer 4

1. signal recognition particle binds to er’s signal sequence and ribosomal subunit stopping translation
2. SRP and SRP receptor binds and the ribosome and the translocon
3. the SRP’s bind a GTP each so pore opens and polypeptide is inserted

Question 5

4-6 steps of signal mechanism

Answer 5

4. GTP hydroylsis releases the SRP
5. signal sequence is cleaved by signal peptidase
6. polypeptide is released in the ER lumen, ribosome is releaseed and translocon pore closes

Question 6

occurs with internal stop transfer sequence and a terminal ER sequence

Answer 6

the stop of the protein halts the translocation and moves to the side in the translocon to anchor the polypeptide so the N-terminus is in the ER lumen and the C-terminus in the cytosol.

Question 7

occurs w single internal start transfer sequence

Answer 7

the polypeptide loops straight thru the channel starting at the sequence

Question 8

N-glycosylation

Answer 8

proteins made at RER cotranslationally by oligosaccharyltransferase (protein complex), they are added to an ASN. Has a nitrogen in the link.

Question 9

where is drug detoxification?

Answer 9

the smooth ER in liver cells, hydroxylation is the first step, the p450 in the liver plays huge role

Question 10

functions of the smooth ER

Answer 10

lipid metabolism, detoxification, caro metabolism, calcium storage, steroid biosynthesis.

Question 11

where are most phospholipids and cholesterol are made ?

Answer 11

on the cytosolic face of ER

Question 12

specifications of lipid biosynthesis

Answer 12

flippases (double membrane), even distribution and asymmetry.

Question 13

Golgi faces, and 2 models of formation

Answer 13

cis- oriented towards ER and trans- face away.
1. stationary cisternae model and cisternal maturation model
membrane incresaes in thickness from 5 to 8nm

Question 14

Anterograde and retrograde transport

Answer 14

anter- ER - golgi - plasma mem.
retro- vesicles from golgi- ER

Question 15

N-linked glycosylation

Answer 15

starts in ER, folds the proteins, and modifies the N-glycosyl group, attaches to serine or threonine.

Question 16

what could keep proteins retained?

Answer 16

kin recognition (cluster to avoid going in vesicles), retention tags keep them in ER ( receptors bind to tags), and retrievel tags, KDEL and KKXX

Question 17

Constitutive secreation and regulated

Answer 17

always on, default pathway, unregulated
regulated- vesicles fuse w mem. w a specific signal, and bud from TGN

Question 18

what is receptor mediated encodytosis

Answer 18

also clathrin dependent endocytosis, need receptors on outer membrane. can hold about 1000 receptors, more than 2 different receptors have been identified

Question 19

low density receptor mediated endocytosis

Answer 19

holds cholesterol

Question 20

caveosomes

Answer 20

lipid rafts

Question 21

all the coat proteins

Answer 21

Clathrin: PS to endosomes
COPI: golgi to ER
COPII: PS to ER

Question 22

clathrin coat

Answer 22

initiated by ARF (GTpase) , dynamin pinches off the coat

Question 23

dynamin

Answer 23

binding domain and GTPase domain

Question 24

COPI and COPII coat

Answer 24

COPI: initiated by ARF protein
COPII: initiation of Sar1

Question 25

Snare

Answer 25

stable and favourable fusion by the interact of v-snare w t-snare, Snap and NSF take it off