Brainscape's Knowledge GenomeTM

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


See full index

CDB > Membrane Trafficking > Flashcards

Membrane Trafficking Flashcards

1
Q

What are the two main cell trafficking routes?

A
  • secretory pathway

- endocytic pathway

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

How is cell trafficking studied?

A
  • Pulse- chase
  • incubate in florescent or media or allow accumulation
  • Chase is then using normal media or removing inhibition for varying periods
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the topologies of the smooth and rough ER?

A
  • Smooth is tubular

- Rough is sheet-like consisting of high density of tubules

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

What occurs in the rough ER?

A
  • lipid biosynthesis
  • protein folding environment
  • ribosomes
  • Oxidising for bisulphide bridge formation
  • Glycosylation, helps folding and chapreon binding
  • Folding quality control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What occurs in the smooth ER?

A
  • Lipid biosynthesis

- ER export

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

What is the ERGIC?

A
  • ER Golgi intermediate
  • COP II vesicles fuse
  • Create vesicular tubular clusters (VTCs)
  • First round of recycling
  • Pulled to golgi with MTs and dyneins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What modifications occurs in the golgi?

A
  • Gradual maturation of cisternae from cis, medial trans

- Protein modification: cleavage, addition or extension of glycans, sugar phosphorylation

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

How does export occur at the trans golgi network?

A
  • Tubes and vesicles being converted to vesicles
  • Point of sorting between proteins
  • Either bulk, directed transport or secretory vesicles which release on signal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How are proteins designated for the ER transfered?

A
  • First part of translation is secretion signal sequence
  • Recognized by signal recognition particle (SRP) which halts translation
  • Binds to SRP receptor and Sec61 translocon in ER membrane
  • Transfered across ER membrane during translation
  • Signal cleaved by signal peptidase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How specific is the ER signal sequence?

A
  • Random combinations work but less efficient

- Requires hydrophobic region

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

How does te Sec61 translocon prevent leaking ions between ER and cytosol?

A
  • Has a plug, only opens when attached to SRP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How are different proteins inserted to the ER?

A
  • Soluble proteins: Signal peptide
  • Single pass membrane protein: signal anchors type I, II
  • Multi pass proteins: signal anchors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is the topology of the protein determined by ER translocon?

A
  • Cleavable vs uncleavable signal sequence/anchor

- Positive charged side stays on cytosolic side

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

How are COPII vesicles made?

A
  • Sec13/31 structural
  • Sec23/23 cargo selective adaptor
  • In vivo starts with GDP-GTP exchange in small GTPase Sar1
  • Cytosolic in D form
  • Recruits Sec23/24, which recruits Sec13/31
  • Sar1 T to D activity acts as timer for uncoating
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How are COPI vesicles made and what signals do they use?

A
  • In ERGIC or golgi
  • Specific ER sequences
  • soluble K/HDEL
  • Type I KKXX
  • Type II RR
  • Arf1 recruits coatomer (structural and recognition)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the role of Erd2 receptor?

A
  • recognizes signals for COPI

- Affinity depends on pH, low pH in golgi means it attaches to cargo and release in ER

17
Q

How do maturing golgi compartments alter composition?

A
  • Sterol and sphingolipid content increases with maturation
  • Allows proteins to sort into prefered environment
  • COPI helps transfer enzymes back
18
Q

How does sorting in the TGN work?

A
  • Secretion default
  • Regulated secretory vesicles sorted by kin recognition, association of multiprotein complex
  • Clathrin coating targets endosomes
19
Q

What are different types of endocytosis?

A
  • Phagocytosis: large particles
  • Pinocytosis: membrane ruffling to take up fluid
  • caveolae: flask shape internative cargo
  • Clathrin coat
20
Q

What are the stages of endosome to lysosome and how do they occur?

A
  • EE receives cargo from plasma membrane and TGN
  • Stops accepting plasma membrane cargo, accumulates LE proteins
  • Acidified due to proton pumps
  • Vesicles bud within LE
  • Fuse with lysosome
21
Q

What kind of fusion events occur between the LE and lysosome?

A
  • Kiss and run, minor exchanges
  • Hybrid organelle formation
  • Then matures back to lysosome
22
Q

How does clathrin mediated vesicle budding occur?

A
  • Cargo selective adaptor protein complex 2 (AP2) and clathrin
  • AP2 complex recognises cytoplasmic tails
  • Due to specificity clathrin coated pits have much higher concentration of product making them efficient
  • GTPase dynamin forms collar and pinches vesicle
  • Shedding coat is ATP dependent, mediated by auxilin and chapeon hsc70
23
Q

How are extracellular nutrients taken up by constitutive receptors?

A
  • Receptors bind to nutrients then use specific cytoplasmic tails to attach to AP-2
  • Once in EE acidity reduces affinity allowing receptor to be recycled
  • Receptors without cargo also internalized
24
Q

How are extracellular nutrients taken up by ligand triggered receptors?

A
  • Only internalize when bound
  • Becomes ubiquinated when binding, targetting it for lysosome
  • In EE ESCRT(0 to III) prevents recycling
  • Then creates intralumen vesicle away from ESCRT to make cargo accessible to lysosome
  • Thereby ESCRT proteins avoid degredation
  • Ex. epidermal growth factor (EGF) recognized by Epsin which binds to AP2
25
Q

How are proteins targeted from the TGN to endosome?

A
  • Ex. lysosomal hydrolase have signal patch
  • Becomes phophorylated in golgi to display mannose-6-phosphate (M6P)
  • M6P binds to clathrin adaptors, AP1 and GGAs
  • Low pH dissociate from protein and recycled using retromer coat
26
Q

What protein coats transport what pathway?

A
  • sec23/24, sec13/31, Sar1 in ER to ERGIC
  • Coatomer, Arf1 in golgi and ERGIC to ER
  • Clathrin, AP1, Arf1 in TGN to endosome
  • AP4 in TGN to autophagosome
  • Retromer or AP5 in endosome to TGN
  • Clathrin, AP-2 dynamin in plasma membrane to EE
27
Q

How many Phosphoinositides (PIPs) can be made and what is their role?

A
  • 7
  • Membrane identity markers, easily converted
  • Provides coincidence detection by join binding with cargo to AP2
28
Q

How does vesicle transport work?

A
  • Mediated by motor proteins and rearrangement of cytoskeleton
29
Q

How are tethers recruited to the right membrane?

A
  • Different GTPases localize to different membranes based on membrane GEFs
  • Recruit diverse Rab effectors, creating a microdomain of specific lipid protein composition
  • GEFs recruit tether
30
Q

What two extra proteins are needed for vesicle fusion?

A
  • ATPase NSF helps uncoil snares

- a-SNAP helps NSF attach

31
Q

What is the SNARE hypothesis?

A
  • SNAREs are SNAP receptors

- For every synaptobrevin there is a syntaxin which are fusogenic

32
Q

How do SNAREs drive membrane fusion?

A
  • Energy release from binding
  • Multiple bind to create trans-SNARE complex
  • Deform membranes
33
Q

How are SNARE’s recycled?

A
  • NSF breakup of SNARE complexes

- Retrograde transport of inactive and active SNAREs

CDB (13 decks)

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