Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCB 2050 > Endomembrane System Part 1 > Flashcards

Endomembrane System Part 1 Flashcards

1
Q

what is the endoplasmic reticulum a starting point for

A

both secretory and biosynthetic pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the ER the site of

A

protein and lipid synthesis
protein folding
processing/quality control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the ER

A

highly complex network of membrane-enclosed, rod-like tubules and sheet like cisternae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what organelle has the largest surface area

A

ER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the lumen

A

aqueous space inside ER tubules and cisternae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what do tubules and cisternae shapes get mediated by

A

reticulons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are cisternae

A

flattened sacs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are in constant flux

A

ER tubules and cisternae - undergo bending, growth/shrinkage, fusion, fission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what does the ER consist of

A

multiple subdomains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

classic examples of subdomains in the ER

A

rough ER
smooth ER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does the RER consist of

A

mostly cisternae with bound ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the RER involved in

A

protein and membrane phospholipid synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does the SER mostly consist of

A

curved tubules lacking ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the SER involved in

A

Ca2+ storage
hormone synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how many other ER subdomains are there

A

> 20

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

nuclear envelope

A

outer nuclear membrane continuous with RER, contains Nups and attached ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the Mitochondria-Associated membrane (MAM)

A

ER region that makes direct contact with mitochondria involved in membrane protein and lipid exchange

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the plasma membrane-associated membrane (PAM)

A

ER region that makes direct contact with the plasma membrane involved in membrane protein and lipid exchange

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are ER exit sites (ERES)

A

ER regions where transport vesicles bud off enroute to Golgi (where vesicles are made)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are free ribosomes in the cytoplasm the fate of

A

nascent, properly folded soluble or membrane bound protein in the cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are the 2 possible fates of free ribosomes in the cytoplasm

A
  1. remain in cytoplasm
  2. targets (post translationally) to proper intracellular compartment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what are ER ‘membrane bound’ ribosomes the fate of

A

nascent, properly folded soluble or membrane protein in RER

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

3 possible fates of ER ‘membrane bound’ ribosomes

A
  1. remains in RER or localizes to another ER subdomain
  2. localizes to other ER derived organelles
  3. targets from ER onto another compartment in endomembrane system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

co-translational translocation of soluble protein in RER lumen

A

protein targeting to and across ER membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

signal sequence in co-translational translocation

A

stretch of 8-15 hydrophobic amino acids - RER targeting signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

signal recognition particle (SRP)

A

ribonucleoprotein particle consists of 6 proteins and 1 small RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

SRP receptor

A

hetero-dimeric ER integral membrane protein complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what do the cytoplasmic-facing domains of SRP receptor serve as

A

docking site for incoming SRP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is the Sec61 translocon

A

multi-protein complex consisting of several ER integral membrane protein subunits (a, B, y)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is the shape of sec61 translocon

A

hourglass shaped aqueous channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what does the hourglass-shaped translocon channel of Sec 61 contain

A

pore ring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is the pore ring in the Sec61 translocon

A

ring of 6 hydrophobic amino acids located at the narrowest diameter of channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what does the pore ring in the Sec61 translocon serve as

A

a gate to seal channel to ions/small molecules to help maintain ER compartmentalization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what is the Sec61 translocon channel also blocked by

A

short alpha-helix plug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what is the short alpha-helix plug in the Sec61 translocon

A

second gate-keeping mechanism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

how does the alpha-helix plug in Sec61 translocon get away from channel

A

during protein translocation the growing polypeptide forces the plug away from channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what is signal peptidase

A

ER integral membrane protein (protease) associated with translocon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

where does signal peptidase face

A

the catalytic domain of signal peptidase faces the ER lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what do reticuloplasmins (ER molecular chaperones) do

A

bind to nascent proteins and mediate proper protein folding and oligomeric assembly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what do reticuloplasmins prevent

A

protein aggregation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

examples of reticuloplasmins

A

BiP
calnexin
calreticulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

membrane protein topology

A

number of membrane-spanning domains and orientation

43
Q

what is transmembrane domain

A

typically alpha-helix of 16-25 hydrophobic amino acids

44
Q

how is the typical TMD favourable

A

energetically favourable with hydrophobic interior of phospholipid bilayer

45
Q

what do ER integral membranes with multiple TMDs lack (Type IV)

A

N-terminal sequence

46
Q

what do multi-spanning ER membrane proteins (Type IV) contain

A

both internal SA sequences and internal STA sequences

47
Q

what is Type 1 membrane protein

A

nascent polypeptide-ribosome complex targets to and associated with translocon

48
Q

what is the comparison between orientations with Type I and Type II membrane proteins

A

opposite orientations

49
Q

does the type II membrane protein have a N-terminal signal sequence

A

no

50
Q

what does Type II membrane protein possess

A

internal signal anchor (SA) sequence

51
Q

comparison between orientations with type III membrane protein

A

same orientation as type I, but like type II, possess internal signal - anchor SA sequence

52
Q

what is the positive outside rule

A

positively charged residues adjacent to TMD determine orientation of TMD/membrane protein

53
Q

where are most membrane proteins and lipids synthesized

A

at ER

54
Q

where do glycolipids get synthesized

A

golgi

55
Q

how are nascent ER membrane proteins and lipids distributed and/or orientated in lipid bilayer

A

asymmetrically

56
Q

integral membrane proteins

A

different regions of protein located on either cytoplasmic or exoplasmic

57
Q

peripheral membrane proteins

A

located on either cytoplasmic or lumenal side of ER membrane

58
Q

membrane phospholipids

A

distributed unequally between cytoplasmic and exoplasmic leaflets of ER membrane bilayer

59
Q

where is protein and lipid asymmetry established

A

ER and are maintained throughout the rest of the endomembrane system

60
Q

what are the 4 final steps in cotranslational-translocation pathway

A
  1. signal sequence cleavage
  2. initial stages of glycolysation
  3. protein folding and assembly
  4. protein quality control
61
Q

what does signal sequence cleavage entail

A

removal of N-terminal signal sequence by signal peptidase

62
Q

what are the initial stages of glycolysation

A

covalent addition of unique carbohydrate side chains carb side chains to specific amino acids of nascent protein

63
Q

what occurs during protein folding and assembly

A

nascent protein folded into proper 3D conformation and oligomeric assembly by molecular chaperones/reticuloplasmins

64
Q

what are most proteins synthesized in ER

A

glycoproteins

65
Q

what are glycoproteins

A

linked to one or more oligosaccharides

66
Q

what are the benefits of glycolysation

A

sugar groups aid in proteins proper folding and serve as binding sites for other macromolecules that interact

67
Q

what is the most common form of glycosylation

A

N-linked glycosylation

68
Q

what is N-linked glycosylation

A

addition of specific short chains of sugar monomers to terminal amino group of asparagine

69
Q

2 staged of N-linked glycosylation

A

core glycosylation
core modification

70
Q

in core glycosylation, what occurs

A

various membrane bound glycosyltransferases synthesize core oligosaccharide

71
Q

what does core glycosylation begin with

A

addition of first sugar to dolichol phosphate

72
Q

what is the final step of core glycosylation

A

transfer of core oligosaccharide from dolichol lipid carrier to nascent soluble/membrane protein while being synthesized

73
Q

in core glycosylation, where does core oligosaccharide get transferred to

A

luminal-facing portions of nascent ER proteins with specific amino acid motif

74
Q

what is the specific amino acid motif in proteins where the core oligosaccharide gets transferred to

A

-N-x-S/T

75
Q

what does tunicamycin do

A

blocks the first step of N-linked glycosylation, preventing proper folding of nascent ER proteins

76
Q

how does tunicamycin block N-linked glycosylation

A

inhibits glycosyltransferase action

77
Q

what is core modification

A

the second stage of N-linked glycosylation

78
Q

what occurs during core modification

A

attached 14-sugar oligosaccharides are sequentially trimmed and modified

79
Q

what gets removed during core modification and by what

A

2 of 3 terminal glucose units by ER lumenal glucosidases

80
Q

in core modification, what is the removal and re-addition of the last glucose unit import for

A

proper protein folding/assembly

81
Q

what does protein disulfide isomerase (PDI) do in core modification

A

catalyzes formation of intra/intermolecular disulphide bonds

82
Q

what else do core oligosaccharides added to the nascent protein during N-linked glycosylation contribute to

A

proper protein folding/assembly and stability
protein quality control

83
Q

what does ER lumen mannosidase do with ER protein quality control

A

removes one mannose unit if protein is properly folded/assembled

84
Q

what recognizes the protein if it is misfiled/misassembled

A

UGGT monitering enzyme (glucosyltransferase)

85
Q

what does the UGGT monitoring enzyme serve as

A

protein conformation sensing protein - usually recognizes hydrophobic residues masked inside correctly folded protein

86
Q

what does UGGT monitoring enzyme do

A

adds back single glucose unit to oligosaccharide core, which then binds to reticuloplasmins to try again

87
Q

how long does ER protein quality control process continue

A

until protein is properly folded, or misfolded proteins are eventually degraded

88
Q

what does the ER-Associated degradation dislocation ERAD do

A

takes misfolded proteins that cannot be fixed and degrades them

89
Q

what does the ERAD pathway involve

A

AAA ATPase p97

90
Q

what is AAA ATPase p97

A

ER membrane protein utilizes ATP hydrolysis to pull misfolded proteins across ER membrane into cytosol

91
Q

during ER protein degradation, what occurs in cytoplasm

A

oligosaccharide chains removed and misfolded protein poly-ubiquitinated

92
Q

what does it mean for the protein to be poly-ubiquitinated

A

protein linked to chain of repeating (poly) ubiquitin units

93
Q

ubiquitin (UB)

A

small (76 amino acids) protein involved in diverse cellular functions

94
Q

mono-UB

A

serves as signal for targeting membrane proteins into intralumenal vesicles of late endosomes/multivesicular bodies

95
Q

poly-UB

A

serves as signal for protein degradation and for most other cellular proteins destined for normal turnover

96
Q

what does poly-UB protein get degraded by

A

proteasome

97
Q

what is a proteasome

A

barrel shaped multisubunit protein-degrading machine located in cytoplasm (and nucleus)

98
Q

what signals Unfolded Protein Response UPR pathways

A

under certain conditions, misfolded/misassembled proteins can accumulate into ER in high levels and overload ERAD which results in ER stress

99
Q

what is each UPR pathway mediated by

A

unique protein sensor - ER integral membrane spanning proteins

100
Q

examples of unique protein sensors that mediate UPRs

A

Ire1
PERK
ATF6

101
Q

what do both PERK and ATF6 possess

A

ER lumenal-facing stress sensing domains

102
Q

form of PERK and ATF6 sensors in non stress conditions

A

inactive by binding to BiP

103
Q

what is eIF2a

A

cytosolic protein translation factor required for initiation of protein synthesis - participates in rmRNA binding

104
Q

ERES-derived transport vesicles

A

move properly-folded proteins out of ER to Golgi and/or other compartments in endomembrane system

MCB 2050 (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions