Endoplasmic Recticulum (ER)

Question 1

ER

Answer 1

• startinf point for scretoru and biosythestic pathway
• lumen is aquaous space inside tubules and citrune

Question 2

reticulons

Answer 2

mediate tubules and cistrnae shape

Question 3

rough ER

Answer 3

• mostly cisternae with bound ribosomes
• protein and membrane phospholobid sythesis

Question 4

smooth ER

Answer 4

• mostlycurved tubules lacking ribosome
• Ca2+ storage
• hormone sythesis

Question 5

nuclear envelope

Answer 5

outer nuclear membrne continous woith RER

Question 6

mitochondria and plasma membrane-associated membranes

Answer 6

ER regions make direct contact with mitochondria or pm

Question 7

ER exit sites

Answer 7

transport vesicles bud off enroute to golgi

Question 8

free ribosmes in cytoplasm

Answer 8

remains in cytoplasm or targets to proper intracellular compartment

Question 9

membrane bound ribosomes

Answer 9

• remains localized in ER subdomain
• localixes to other ER derived organelles
• goes from ER to ? endomembrane compartment

Question 10

cotranslation of soluble protein into RER lumen

Answer 10

• in cytoplasm tranlation of ribisome begins
• N terminus emerges containing signal sequence
• recognized by signal recognition protein which bind and stips translation
• SRP binds to receptor (RER surface)
• GTP hydrolysis release SRP
• polypeptide and ribsome transferred to cytoplasmic side of sec 61 translocon
• n terminus inserted into opening of tanslocon channel
• signal peptidase cleaves N terminus into lumen
• protein enters lumen and pre closes

Question 11

sec 61 translocon

Answer 11

contains pore ring

Question 12

membrane protein topology

Answer 12

of membrane spanning domains and orientation

Question 13

tran membrane doemain

Question 14

single pas integral membrane protein

Answer 14

Type l (STA)
Type ll (SA)
Type ll (SA)

Question 15

Multi-spanning integral membrane protein

Answer 15

type lV (STA and SA)

Question 16

stop transfer anchor vs signal anchor

Answer 16

stop (STA)
signal (SA)

Question 17

positive outside rule

Question 18

membrane bilayer asymetry

Answer 18

• membrane proteins and lipids distribited in nilayer aymetry
• exoplamic
• cytoplasmic

Question 19

glycosylations

Answer 19

most proteins sythesized in ER are glycoproteins linked to one or more sugar chains

Question 20

N linked glycosylation

Answer 20

(addition of sepcific chains foo sugaR monomer)
1) core glycosyltrone: glycoytranferase senthisizes core oligosaccharides
2) core modification
3) tranfer core oligosachride from diolchol lipid carrier to nacsent soluble protein (specific aa seq, -N-X-Sh-)
4) 2/3 terminal glucose unites removed by glucocidses

Question 21

protein disulfied isomerse (PDI)

Answer 21

catalyizes formation of intra/intermolecular disulfide bonds

Question 22

ER protein quality control

Answer 22

rectoplasmins and PDI help mediate proper foldinf and stability
oligomeric assembly

Question 23

if a protein is properlu folded one manlose unit removed by er mamolidase and

Answer 23

becomes er resident
goes to golgi

Question 24

UGGT monitoring enzyme

Answer 24

• recongnizes if protein is released from retocplasmins is misfolded
• adds back single glucose to oligosachride core
• binds back to calexon

Question 25

ER protein degredation

Answer 25

- AAA ATPase p97 (ATP hydrolisis pull misfolded proteins across membrane into cytosol) - into cytoplasm oligosacride removed and misfolded by poly ubiquitin

Question 26

mono UB

Answer 26

- signal for targetinf membrane proteins

Question 27

poly UB

Answer 27

signal for degradation and degrade by protesomes

Question 28

protesome

Answer 28

- barrel shapped multi subunit degradifinf machine in cytoplasm - bind cap or lib - poly UB removed (recycled) - protein threaded into prelesome degradation prokeolisis

Question 29

unfolded protein response pathway (UPR)

Answer 29

to much misfolded proteins in er er stress Ire1 Perk Atrg all regulate different pathway (Perk and Atrg stress sensing domain inactive by Bio)

Question 30

Perk mediated UPR pathway

Answer 30

- Bip release - perk dimerizes (active) - phosporylate eIF2a (stops protein synthesis) - chaperones (bip available to focus on misfolded proteins)

Question 31

ATF6 mediated UPR pathway

Answer 31

- Bip Release - active AFF goes ER -> Golgi - trancription factor domain cleaved by golgu acociated protease - strand factor target nulcease upregulates genes encoding key proteins in quaternary control

Question 32

ER exit sites (ERes)

Answer 32

- subdomain of ER located next to cis face of gGolfi complex - responsible for budding to send to golgi

Question 33

COat proteins (COPs)

Answer 33

- assemle on cytpoplasmic surface of ERes 1) mediate membrane curvature and formation of vesicles 2) recognize and concentrate specific cargo components into vesicle

Question 34

COPll

Answer 34

move ER to Golgi

Question 35

COPl

Answer 35

move backward Golgi to ER

Question 36

clathrin

Answer 36

- golgi->Golgi-> ER - plasma membrane -> endosomes

Question 37

retrograde transport

Question 38

COPll assembly

Answer 38

Sar1 reqruited - binds to sec12 (guanosine exchange factor GDP->GTP) - SAR 1 binding to GTP binding causes conformational change (exposes N terminus Sar 1 GTP integrated into cytoplasmic facing leaflet of ERes membrane bulayer Sar 1 GTO binds to other copll - recruits sec23 and sec 24 (promote bending)

Question 39

Anterograde vs retrograde vesicle transport

Question 40

vesicle docking and fusion at CGN

Answer 40

- mediated by Rab proteins - rabs and rab effector binding conveys vesicke targetinf specifity and docking

Question 41

snare proteins

Answer 41

- after dockinf they initiate fusion v snare: on transport vesicle T snare: on target AA receptor both interact with snare complex

Question 42

snare motif

Answer 42

cytoplasmic facing coiled coil domain in V and Extend from vesicle target

Question 43

membrane fusion occurs when...

Answer 43

NSF and SNAP mediate disasembly of snare complex

Question 44

ER rtreval sorting signalinf

Answer 44

c terminal - kdel sequence and ce terminal siysre sequence

Question 45

kdel receptor

Answer 45

recognixe escaped soluble ER proteins