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Biochemistry and Cell Biology Semester 1 > Protein folding > Flashcards

Protein folding Flashcards

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1
Q

endoplasmic reticulum features

A

continuous with outer membrane
tubules which extend through cytoplasm

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2
Q

2 types of ER

A

smooth - lipid synthesis
rough - protein synthesis

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3
Q

RER function

A

synthesis of 2 types of protein - transmembrane and secretion proteins

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4
Q

how are proteins transported into er

A

co translational translocation

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5
Q

why is there no chaperone protein in co translational translocation

A

one end of the protein attached to ribosome while other inserts into er (remains in primary sequence)

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6
Q

role of chaperone proteins

A

bind and escort proteins to mitochondria to prevent damage and folding

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7
Q

signal recognition particle (SRP)

A

recognises signal sequence on N terminal binding to it and the ribosome (pauses synthesis by binding to pause domain)

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8
Q

purpose of the hinge in SRP

A

allows binding to protein and ribosome

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9
Q

for co translation translocation the signal sequence must be…

A

recognised by er and embedded in er membrane

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10
Q

final steps of co translational translocation

A

once translated, mRNA released back into free ribosome pool

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11
Q

where do proteins go after they are translated

A

released = fully transported by exocytosis into er lumen
membrane = embedded in er membrane

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12
Q

what happens inside er

A

modification
glycosylation

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13
Q

glycosylation

A

adding 14 sugar to N terminus of asparagine side chain of a protein if cannot be folded

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14
Q

importance of glycosylation

A

quality control, recognition, protection

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15
Q

quality control

A
  1. if not folded, 3 glucose and 1 mannose cleaved from N linked oligosaccharide
  2. if not folded glucosyl transferase enzymes add 1 glucose back (proteostasis)
  3. calnexin binds to unfolded protein to prevent aggregation
  4. remove terminal glucose by glucosidase causes release of protein from calnexin
  5. glucosyl transferase determine if folded right and if not repeats
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16
Q

calnexin

A

er membrane bound cho binding chaperone protein

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17
Q

purpose of single glucose addition

A

message to calnexin

18
Q

if a protein remains misfolded …

A

it will be released from er and targeted for degradation

19
Q

what happens if misfolded proteins accumulate

A

causes er stress and trigger unfolded protein response (UPR)

20
Q

UPR

A

inhibits protein synthesis
degrade misfolded proteins
increase transcription of chaperones

21
Q

role of PERK and IRE1 and ATF6 in UPR

A

PERK = pauses translation
IRE1 and ATF6 = degradation and activation of genes to increase folding capacity

22
Q

3 types of vesicle

A

COPII coated vesicle (from er) EXOCYTOSIS
COPI coated vesicle (from Golgi) ENDOCYTOSIS
Cathrin coated vesicle (from plasma membrane and between Golgi and endosomes)

23
Q

importance of vesicle coating

A

ensure specificity and find right membrane

24
Q

role of GTP and GDP in vesicles

A

GTP bound = active
GDP bound = inactive

25
Q

process of release of vesicles

A

GEF on membrane activate Rab GTP
Rab GTP bind to Rab effector protein on target membrane
causes tethering of vesicles to target membrane

26
Q

what proteins are involved in membrane fusion

A

V-SNARES (vesicles) and T SNARES (target)

27
Q

how to V and T SNARES work

A

specific to each other and wrap around each other to form a stable trans SNARE complex which bring the vesicle and membrane within 1.5nm

28
Q

process of membrane fusion

A

Rab GAP causes Rab to hydrolyse GTP to GDP
Rab GDP released from vesicle and bound by Rab GTP dissociation inhibitor to keep Ra inactive

29
Q

ER - Golgi

A

multiple vesicles fuse to form vesicular tubular cutters

30
Q

what’s the purpose of a retrieval pathway

A

receptors NSAREs or proteins taken up by accident can be returned to ER

31
Q

what is the Golgi

A

stack of flattened membrane enclosed compartments called cistemae

32
Q

unction

A
33
Q

function of Golgi

A

promote correct folding of proteins
prevent unwanted aggregation
act as signals for sorting and targeting correct pathway

34
Q

Golgi - lysosomes

A
35
Q

what’s a lysosome

A

degradative organelles (digest unwanted material)
contain enzymes to break down macromolecules
only active at 4.5-5 ph

36
Q

how’s ph of lysosomes maintained

A

by vacuolar ATPase

37
Q

endosomes and lysosomes

A

late endosome contains ingested material
fuses with lysosome forming endolysosome
once digestion completes lysosomes form

38
Q

purpose of lysosomes having mannose 6 phosphate tag

A

direct protein to lysosomal network

39
Q

endocytosis

A

transport into cell from plasma membrane

40
Q

what happens to ingested material once endocytic vesicle fuses with early endosome

A

degraded using hydrolyses
recycled

41
Q

2 types of exocytotic pathways

A

released all at once
selective (maintained din vesicle until needed)

Biochemistry and Cell Biology Semester 1 (12 decks)

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