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Golgi Apparatus & Vesicular Traffic (14) Flashcards

1
Q

location of golgi

A

b/w the ER & cell surface

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2
Q

structure of golgi

A

membrane-bound stacks called cisternae

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3
Q

function of golgi

A

modify & sort PROs for export or for other organelles, tag PROs ensuring they go to the correct location

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4
Q

how are the stacks of the Golgi named?

A

their proximity to the ER

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5
Q

trans-Golgi network

A

vesicles that bud off of Golgi & move to diff places in the cell

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6
Q

how do the cisternae layers differ among each other?

A

each department has unique enzymes

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7
Q

how can the Golgi be studied?

A

electron microscope

staining the layers based on their diffs in enzyme composition

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8
Q

Cis region

A

sugars & PROs are phosphorylated

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9
Q

medial region

A

have enzymes that remove carbs that were added in the ER & then add new carbs

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10
Q

trans region

A

area where lysosomes are sorted

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11
Q

what enzyme is the trans region rich of?

A

acid phosphatase`

enzyme found in lysosomes

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12
Q

N linked glycoPROs

A

sugars attached at the N of the asparagine

Begins in ER & continues in Golgi 

Glycosyltransferases facilitate the attachments
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13
Q

Glycosyltransferase

A

add sugars to the N of aspargine in N linked glycoPROs

found in the Golgi

act in a rigidly determine sequence

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14
Q

O-linked glycoPROs

A

sugars attached to the O of serine of threonine

occurs only in the Golgi

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15
Q

what is the diff b/w O-linked & N-linked glycoPROs?

A

attachment of the sugar: N –> N of asparagine & O –> O of serine or threonine

Location of attachment: N –> Golgi & ER & O –> Golgi only

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16
Q

how does glycosylation of PROs effect their solubility?

A

more hydrophilic & therefore, increases solubility

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17
Q

Glycosylating PROs allows them to bind where?

A

extracellular matrix

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18
Q

what is a way for PROs to have more specific interactions?

A

through glycoPROs

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19
Q

why glycosylate PROs?

A

Increases their solubility by making them hydrophilic

Enables binding to the extracellular matrix

Reduces susceptibility to proteases, carbs act as a physical barrier protecting the PRO core
Protects cell surface

Structural complexity to the PRO
New function
Provides more specific interactions with other PROs

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20
Q

where do we see an abundance of glycosylated PROs?

A

cell’s surface where cell-to-cell interactions occur

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21
Q

what creates diversity of AAs?

A

phosphorylation & glycosylation

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22
Q

what contents move through the Golgi?

A

membranes including PROs, phosphoglycerides & other membrane lipids

vesicles including PROs being processed & enzymes doing the processing

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23
Q

transient/anterograde movement

A

forward

cis to trans

24
Q

retrograde movement

A

trans to cis

reverse

25
cisternal maturation model. When does this occur? & how?
each cisternae is physical moved up the stack & changes composition Enzymes seem localized to departments but vesicles can come & go Maturation process New vesicles form causing upwards movements Done when macromolecules require transport (can’t fit in vesicles)
26
vesicular transport model
materials in the interior & in the membrane are brought up to next cisternae by vesicle transport vesicles bud off cis & then fuse with medial etc.
27
what evidence is provided for the vesicular transport model?
vesicles were found to move both forward & backwards so they could maintain enzymes diffs
28
what evidence is provided for the cisternal maturation model?
there are some materials that are never seen in vesicles including large molecules
29
how do vesicles travel?
along microtubules, anchored by PROs including dynactin
30
how do vesicles move?
travel along microtubules dyenin can grab dynactin & pull the vesicle with it Kinesin use other adaptor PROs recognizing PROs in the membrane
31
when does the Golgi break up?
onset of mitosis during nuclear membrane degradation (prophase)
32
when does the Golgi reappear in mitosis? & How?
telophase Still UK but, growing microtubules may collect & algin small vesicles which later fuse together creating cisternae
33
what is the role of coat PROs in vesicle formation?
mechanical force
34
what is the role of integral PROs in vesicle formation?
selection of cargo
35
what are the PROs found in a vesicle?
integral PROs binding cargo & other PROs to connect with the coat
36
what are the 3 functions of the vesicles integral & peripheral PROs?
vesicle formation/budding selection of vesicle contents by receptor sys recognition & fusing target membrane
37
COP II coated vesicles
forward movement from ER & b/w cisternae o Anterograde movement o Cis – medial – trans – OT
38
COP I coated vesicles
retrograde movement from TGN to Golgi to RER Trans – medial – cis … maybe back to ER
39
clathrin-coated vesicles
TGN to lysosomes & endocytosis Assoc with movement of vesicles from trans Golgi to other places
40
bulk flow
non-specific contents are captured during vesicle formation ex: water
41
what types of contents are found in vesicles?
bulk flow specific materials
42
vesicle formation process
Receptor PRO with specificity to specific cargo Will recruit PROs to help build coat Coat will build vesicle Vesicle will bud off Vesicle will move to Golgi via motor PROs
43
what are the requirements of vesicular transport?
selection of contents (receptor-mediated) production of vesicles (PRO coat) movement of vesicle (tethering/docking & membrane fusion)
44
how do vesicle select their cargo?
``` Receptors select & carry contents High specificity & affinity for cargo & its target molecule Integral PROs (ligand with cargo) ``` The target molecule is at low concentrations in the mixture, the receptor picks it out For every cargo molecule there is a receptor holding it in place (1:1)
45
How do vesicles bud off?
Coat PROs assemble at the membrane forcing the bilayer to bend Coat PROs help gather the receptors that will carry the cargo Shortly after the vesicle pinches off, the coat falls off & the vesicle is ready to travel to its destination
46
steps in COP II coated vesicles
1. Receptors bind selected PROs (cargo) within the lumen of the RER & assembles 2 PROs: coat PRO & GTPase Sar1 PROs destined for secretion ER resident PROs such as BiP are left behind 2. Sar1, a GTP binding PRO, if active promotes assembly of the coat 3. Coat PROs bind to cytosol side of specific receptor in RER membrane, vesicle form determined by steric hindrance of coat PROs 4. Coated bud forms & leaves the RER Taking along receptor/cargo complexes Also some membrane PROs (ex: Golgi glycosyltransferases) Also membrane PROs involved in docking/fusion: destination tags Rab & SNARES (not shown) 5. Sar1 hydrolyzes the GTP GDP becoming inactive 6. Disassembly of the coat (Sar1) Things in the lumen of the vesicle & in the membrane stay there Membrane-bound PRO but not integral Leaves the membrane Has a branch that pokes outside the membrane, GTP hydrolyzes occurs & causes it to change shape 7. The vesicle is now able to fuse with the cis Golgi (vesicles are no longer coated)
47
What activates Sar1?
attachment to GTP
48
what inactivates Sar1?
GTP --> GDP
49
what does a budded vesicle contain in COP II vesicles?
Taking along receptor/cargo complexes Also some membrane PROs (ex: Golgi glycosyltransferases) Also membrane PROs involved in docking/fusion: destination tags Rab & SNARES (not shown)
50
what causes the coat PRO to fall off in COP II vesicles?
GTP --> GDP causing a change in shape
51
What components required for the formation of COP II vesicles?
Receptors to bind cargo Coat PRO GTPase Sar1 promoting the assembly & disassembly of the coat PRO Destination tags for docking/fusion (Rab & SNARES)
52
what is required for a coat PRO to recognize a receptor?
ligand bound to a receptor
53
What determines which PROs enter COP I vesicles?
PROs contain retrieval signals which are recognized by the receptor in the COP I membranes
54
what signal is recognized by COP I receptors on soluble PROs?
KDEL
55
what signal is recognized by COP I receptors on membrane PROs?
KKXX
56
How does COP I look for KDEL receptors?
looks for KKXX sequence

C Bio (30 decks)

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