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Biochemistry > Week 8 pt II - And Exocytosis > Flashcards

Week 8 pt II - And Exocytosis Flashcards

1
Q

COPI vesicles

A

Recruitment of GTPase called SARI into ER membrane

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2
Q

What happens when there is GTP to GDP exchange?

A

It sticks out amphiphilic alpha helix that is integrated into the membrane
Starts the membrane curvature

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3
Q

What are examples of COP proteins?

A

COP16

COP24

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4
Q

What is the outer code?

A

COP30

COP31

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5
Q

What occurs after the outer code?

A

The vesicles will bud off

It has to lose the protein coat before it can fuse with the target membrane (occurs by GTP hydrolysis)

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6
Q

What are COPI vesicles?

A

Vesicles that bring back from the Golgi to the ER

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7
Q

What does COPI vesicles bring?

A

Stuff from Trans Golgi back to Cis Golgi

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8
Q

What are the enzymes that are necessary for the Golgi to perform its function?

A

Manase

Glycosyl transferase

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9
Q

How are Manase and glycosyl transferase recruited?

A

Through receptors and binding proteins

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10
Q

What is Arf1?

A

GTPases related to group of proteins called Ras proteins

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11
Q

What happens when GTP is hydrolysed to GDP?

A

The protein coat is lost

COP1 vesicles can fuse very easily with ER

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12
Q

How was COP vesicles discovered?

A

Fed mammalian cells with non-hydrolysable GTP

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13
Q

What binds GTP?

A

ARf1 and SAR1

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14
Q

What does ARf1 and SAR1 do?

A

Recruit all the proteins and form vesicles
GTP cannot be hydrolysed
Protein coat is not lost
Don’t get fusion with any other membrane

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15
Q

What was observed when cell lines were fed with non-hydrolysable GTP?

A

Massive build up of vesicles all throughout the cell

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16
Q

Trans Golgi Network

A

Sorting of things, anything that leaves the Golgi and goes through lysosomes

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17
Q

What occurs at Trans Golgi Network?

A

Things going to the plasma membrane to export proteins
Things going to form lysosomes
Constitutive export and regulated export

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18
Q

What do Lysosomes Contain?

A

Nearly 50 hydrolytic enzymes
Specialised for breaking different kinds of binds
Destroying different types of Proteins and lipids

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19
Q

What are the hydrolytic enzymes never allowed to touch?

A

Cytosol

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20
Q

When are the hydrolytic enzymes active ?

A

At very acidic PH (acidic hydrolases)

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21
Q

Where are the hydrolytic enzymes initially synthesised?

A

ER and Golgi (PH is neutral)

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22
Q

What does Golgi add?

A

Further processing to the Mannose chains to produce the unique signature for lysosomes

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23
Q

Where are lysosomal proteins synthesised and delivered to?

A

Synthesised: ER
Delivery: lysosome

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24
Q

What happens in the Golgi complex (cis-cisternae)?

A

Lysosomal enzymes are recognised by enzymes that catalyse the two step addition of phosphate group to mannose sugars of N-linked carbohydrate chains

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25
Q

What are the enzymes that catalyse the two step addition of phosphate group to Mannose sugars?

A

N-Acetylglucosamine

Phosphodiester glycosidase

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26
Q

What does N-Acetylglucosamine phosphotransferase do?

A

Transfers 2 N-acetylglucosamine from a nucleotide sugar donor phosphate to Mannose residues of N-linked oligosaccahrides

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27
Q

What is UDP glucose used for?

A

Form a phosphodiester bond with one of Mannose residues

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28
Q

What does phosphodiester glycosidase enzyme cleave?

A

2 glucosamine

Mannose 6-phosphate residues as part of the oligosaccharide chain

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29
Q

What is the signature for lysosomes?

A

Mannose 6-phosphate motifs

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30
Q

Mannose 6-phosphate receptors

A

Interact specifically with lysosomal enzymes on luminal side of the vesicle
Interact specifically with adaptors on the cytosolic surface of vesicle

31
Q

What is the result of M6PR on TGN membrane?

A

Lysosome enzyme on TGN become concentrated into clathrin coated vesicles

32
Q

What do clathrin coat form?

A

Vesicles which bud off after formation of clathrin cage

Migrate the vesicle to the cytosol until they fuse with a late endosomes

33
Q

Why are Mannose 6-phosphate receptor present in the plasma membrane?

A

Capture lysosomal enzymes that are secreted into extracellular space
Return the enzymes to a pathway that directs them to a lysosome

34
Q

The vesicles released from Golgi Contain?

A

Proton pump that use the energy of ATP to transport hydrogen ions from cytoplasm to the interior

35
Q

What happens as the vesicle travels in the cytoplasm?

A

PH drops

36
Q

What is the PH of late endosomes?

A

Lower than that of Golgi

37
Q

What does change in PH used by?

A

Cell to recycle the receptors of lysosomal enzymes

38
Q

What is the binding affinity of the receptors for Mannose 6-phosphate m?

A

Very PH sensitive in the mild acidic range

39
Q

What happens at PH 6.5?

A

Endosomes release lysosomal enzymes
Destabilise the structure of Mannose phosphate receptor
Disrupts the interaction between lysosomes and mannose phosphate receptor

40
Q

What does the proton pump in the membrane of lysosomes keep the PH around?

A

5

41
Q

What are the lysosomal enzymes bound onto?

A

Mannose 6 phosphate receptor

42
Q

What is the name of the Adaptor?

A

Golgi associated gamma adaptin (GGA)

43
Q

What is the microtubule directly stretched between?

A

Organelles

44
Q

What is found within microtubules?

A

Big bulges of vesicles

The smaller one travelling up the thin horizontal

45
Q

What do vesicles move along?

A

Microtubule

46
Q

What is Hand over slide (Hamburg)?

A

Beta tubulin on the microtubule
ATP hydrolysis and one foot goes over and next foot slides along
The red foot moved over and stored kinetic energy and the blue foot slides across
Happens at molecular level

47
Q

Hand over hand

A

Kinesin molecules walk down the microtubule inside the cell transporting its cargo
The adaptor is attached to gigantic vesicle

48
Q

How does HIV get to the nucleus?

A

On Dynein and kinesin

Motor proteins

49
Q

What does Fibrous Tethering protein mediate?

A

Initial contact between transport vesicles and it’s target membrane

50
Q

Fibrous tethering proteins

A

Form molecular bridge between two Membranes over a large distance (50-200nm)

51
Q

What is tethering?

A

Early stage of vesicle fusion that requires specificity between vesicle and target membrane

52
Q

What are RAB proteins on vesicle and target membrane involved in?

A

Recruiting specific tethering proteins that mediate initial contact between two Membranes

53
Q

What does SNARES mediate?

A

Vesicle fusion

54
Q

What do SNARE proteins have?

A

More than 35 membrane proteins

55
Q

What does SNARE motif consist of?

A

60-70 amino acids which can form a complex with another SNARE motif

56
Q

What is the most studied SNARE proteins?

A

Mediating rocking of synaptic vesicles with presynaptic membrane during the release of a NT

57
Q

What are the two types of SNARES?

A

V-snares

T-snares

58
Q

What is V-snare?

A

Incorporated into vesicle during budding (synaptobrevin)

59
Q

What is T snare?

A

Located on the target membrane surface (SNAP-25 and syntaxin)

60
Q

What happens in synapses and epithelial cells?

A

Regulated exocytosis contents being released into the environment

61
Q

What is Kidd and Release model?

A

The vesicle bind very briefly

Opening up of the pore and the content is released and the vesicle can move away

62
Q

Why do all cells endocytose constantly?

A

To replace things in the plasma membrane
Refresh lipids
Change structure

63
Q

What is receptor mediated endocytosis?

A

The receptor bind cargo proteins
Outside: start of a indent
High density: concentrated yolk protein being accumulated in the life of the start of the formation of vesicle
Greater density on the inside of cell on other side of membrane - assembly of the protein coat to produce new vesicles
Vesicle pinching: dense coat on inside and concentrated cargo on the outside of cell

64
Q

What is Latrice made up from?

A

Protein called clathrin

65
Q

What is clathrin made up of?

A

Triskelion

66
Q

What does Triskelion Contain?

A

3 heavy chain

2 light chain

67
Q

What is the lumen of endosomes acidified by?

A

H+-ATPase

68
Q

Where is early endosomes located?

A

Near cell periphery

69
Q

What do early endosomes do?

A

Sort Materials

Send bound ligands to the late endosomes

70
Q

Where are late endosomes located?

A

Near the nucleus

71
Q

What are late endosomes known as?

A

Multivesicular bodies (MVBs)

72
Q

What are the properties of signalling receptors?

A

Bind to extracellular ligand that carry messages
Marked for endocytosis by ubiquitination
Sorted into membrane that form internal vesicles in late endosomes
Late endosomes fuse with Lysosomes where receptors are degraded

73
Q

What are the properties of house keeping receptors ?

A

Responsible for uptake of materials
Dissociation from bound ligands triggered by low PH in endosomes
Recycled to the plasma membrane

Biochemistry (15 decks)

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