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Cell Biology > ER, Golgi, Lysosomes & Endocytosis > Flashcards

ER, Golgi, Lysosomes & Endocytosis Flashcards

1
Q

endomembrane system components

A 
ER
Golgi
endosomes
lysosomes
cell surface
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2
Q

Rough ER has:

A

ribosomes

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3
Q

Protein targeted to ER recognised by:

A

signal sequence which is part of growing polypeptide chain

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4
Q

Signal sequence recognised by:

A

Signal recognition particle (SRP)

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5
Q

SRP binds to:

A

SRP receptor in ER membrane

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6
Q

SRP receptor recruits:

A

Translocation channel

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7
Q

Co-translational translocation transports ______ proteins into _______ & cleaves signal peptide with ______

A

soluble
ER lumen
signal peptidase

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8
Q

Start-transfer and stop-transfer sequences are important for translocation of:

A

transmembrane and multi-pass membrane protein

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9
Q

ER functions (2)

A
  • disulphide bridge formation

- N-glycosylation

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10
Q

Export from the ER is highly ______

A

regulated

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11
Q

Chaperone proteins responsible for

A

protein folding

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12
Q

Unfolded protein response

A

presence of unfolded protein trigger chaperone protein production and ER expansion
(feedback response)

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13
Q

Retention in ER

A

some soluble proteins like chaperones have a KDEL C-terminal tag which allows them to remain in the ER

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14
Q

Vesicle coat functions (2)

A
  1. concentrates specific membrane proteins in specialised patch, creating vesicle membrane
  2. moulds forming vesicle
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15
Q

3 main coats:

A
  • clathrin
  • COPI
  • COPII
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16
Q

clathrin coated vesicles transport

A

from Golgi

from plasma membrane

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17
Q

COPI & COPII coated vesicle transport

A

from ER

from Golgi cisternae

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18
Q

coat assembly controlled by:

A

monomeric GTPases

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19
Q

GTP-bound:

GDP-bound:

A

active

inactive

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20
Q

GTP-binding proteins activated by ______ and inactivated by ______

A

GEFs

GAPs

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21
Q

coat recruitment GTPase that controls COPII assembly on ER membrane

A

Sar1

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22
Q

COPII vesicle formation:

A

Sar1 binds to Sar1-GEF embedded in ER membrane which causes Sar1 to bind GTP and become active

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23
Q

Active Sar1

A

inserts amphipathic helix into cytoplasmic leaflet of ER membrane and is ready to recruit coat protein like Sec23 & Sec24

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24
Q

Outer coat of COPII formed by

A

Sec13/31 which assembles the vesicle into a symmetrical cage

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25
Q

coat disassembly

A

hydrolysis of bound GTP to GDP

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26
Q

Rab proteins

A
  • guide vesicle targeting
  • monomeric GTPases
  • cycle between membrane and cytosol
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27
Q

GDP-bound Rab

A

inactive and bound to GDI

28
Q

GTP-bound Rab

A

active and tightly associated with a membrane

29
Q

SNARE proteins mediate:

A

membrane fusion

30
Q

3 types of SNARE protein

A

V-SNARES
T-SNARES
Q-SNARES

31
Q

SNARE protein structure

A

alpha helical domains which form a 4-helix bundle resulting in a trans-SNARE-complex

32
Q

trans-SNARE-complexes have to disassemble, which is catalysed by:

A

NSF (ATPase)

33
Q

Coats for anterograde and retrograde transport:

A

Antero: COPII
Retro: COPI

34
Q

In the Golgi, transported molecules undergo an ordered series of:

A

covalent modifications

35
Q

cis-Golgi-network (CGN)

A

collection of fused vesicles arriving from ER

36
Q

trans-Golgi-network (TGN)

A

where proteins exit the Golgi in vesicles bound for cell surface or another compartment

37
Q

constitutive secretion

A

vesicles move directly from Golgi to plasma membrane

38
Q

regulated secretion

A

fusion of vesicles with plasma membrane depends on a signal

39
Q

Lysosomes

A

membrane-bound sacs of hydrolytic enzymes

40
Q

At what pH do acid hydrolases function?

41
Q

acid hydrolases e.g.

A 
nucleases
proteases
glycosidases
lipases
phosphatases
sulfatases
phospholipases
42
Q

acidic pH in lysosome maintained by:

A

H+ influx into lumen by vacuolar H+ ATPases

43
Q

Metabolic transportes in lysosomal membranes deliver:

A

sugars, amino acids, nucleotides… back into cytoplasm

44
Q

Lysosomal functions (3)

A
  • endocytosis
  • autophagy
  • phagocytosis
45
Q

lysosomal protein signal

A

mannose-6-phosphate

46
Q

M6P groups added exclusively to:

A

N-linked oligosaccharides of lysosomal enzymes

47
Q

M6P recognised by ___ in __

A

M6P receptor protein

TGN

48
Q

TGN packages lysosomal protein into _____ coated vesicles which are delivered to _____

A

clathrin

early endosomes

49
Q

addition of M6P groups catalysed by:

A

GlcNAc phosphotransferase

50
Q

When GlcNAc is cleaved off it leaves:

A

M6P signal marker

51
Q

lysosomal storage diseases:

A

I-cell disease

mucolipidosis

52
Q

clathrin-coated vesicle structure

A

3 large and 3 small subunits form triskelions which assemble into a convex framework of pentagons and hexagons

53
Q

adaptor protein in clathrin-coated vesicles

A

form discrete 2nd layer of coat between clathrin cage and membrane which traps transmembrane proteins that capture cargo in vesicle

54
Q

dynamin

A
  • forms spring-like as clathrin-coated vesicle is forming

- GTP hydrolysis causes conformational change which separates vesicle from membrane

55
Q

macrophages

A

defend against infection by ingesting invading microorganisms and digesting them with lysosomal enzymes

56
Q

macromolecules bind to complementary transmembrane receptor protein, accumulate in clathrin-coated pits and enter cell as receptor-macromolecule complexes

A

receptor mediated endocytosis

57
Q

Receptor mediated endocytosis examples

A
  • LDL receptor
  • Transferrin receptor
  • EGF receptor
58
Q

Lipoprotein particles are bound by:

A

Apoprotein B-100

59
Q

Transferrin cycle

A

gets iron into cell

60
Q

epidermal growth factor (EGF)

A

small signal protein that causes epidermal cells amongst others to divide

61
Q

When EGF binds to receptor:

A
  • receptor becomes a dimer, which activates its’ enzyme activity
  • tyrosine kinase phosphorylates itself
  • cells proliferate
62
Q

Mutated EGF receptor

A

proto-oncogene

63
Q

breakdown of membrane spanning protein with signalling end on cytosolic side involve:

A

multi-vesicular bodies

64
Q

(multi-vesicular bodies) vesicles produced into endosomes with help of:

A
  • ubiquitin tags

- Escrt complexes

65
Q

multi-vesicular bodies break what rule?

A

topology rule

Cell Biology (8 decks)

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