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BSCI330 SPRING > exam 3 vesicular transport > Flashcards

exam 3 vesicular transport Flashcards

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1
Q

what occurs via vesicular transport

A

movement of proteins between the ER, most membranous organelles, and the cell surface

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2
Q

what do proteins have to undergo before using vesicular transport to get into ER

A

undergo transmembrane transport

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3
Q

what are proteins transported by in vesicular transport

A

transported by vesicles, which bud off of one organelle and fuse with another and deliver contents that way

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4
Q

what are proteins guided by

A

specific coat and targeting proteins

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5
Q

what do retrograde pathways do

A

they are reverse pathways that allow the return of “escaped” proteins to original organelles and the recycling of targeting proteins

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6
Q

what serves as roadways for vesicular transport

A

cytoskeleton

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7
Q

why do proteins never have to cross a membrane from one side to the other using vesicular transport

A

vesicular transport keeps topological similarities

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8
Q

what does vesicular sorting depend on

A

the assembly of a special protein coat formed at specific locations along a given donor compartment

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9
Q

what do coat proteins do

A

deform membrane to start vesicular formation and initiate targeting to next compartment

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10
Q

what are the 3 main classes of coat proteins

A

COPI, COPII, clathrin

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11
Q

what is COPII used in

A

coating vesicles that bud off of ER and go to golgi

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12
Q

what is COPI used for

A

vesicles that bud off of golgi and move internally or go to ER and plasma membrane

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13
Q

what is clathrin used for

A

transport between cell surface, golgi, and endosomes

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14
Q

what represents the initial step in vesicle formation

A

coat proteins

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15
Q

what do transport vesicles bud off as

A

as coated vesicles that have a distinctive cage of proteins covering their cytosolic surface

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16
Q

what closes off membrane into spherical vesicle

A

a forced curvature of membrane due to coat proteins - before the vesicle fuses with a target membrane, the coat is discarded to allow the two cytosolic membrane surfaces to interact directly and fuse

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17
Q

what marks organelles and membrane domains

A

phospholipids containing inositol head groups

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18
Q

how do coat proteins know where they are

A

lipid concentrations are different in different domains

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19
Q

what/where can inositol get phosphorylated by

A

inositol can get phosphorylated at various locations by different lipid kinases

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20
Q

what can different phosphorylations be recognized by

A

other proteins, which can then tag membranes to identify them - kinases are selectively associated with different membranes

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21
Q

what can phosphoinositides recruit

A

various proteins that possess lipid binding domains (which only recognize a specific type of PI)

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22
Q

how can binding be regulated

A

by phosphorylating or dephosphorylating polar head groups

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23
Q

what do adapter proteins bind to

A

membrane proteins or membrane to recruit coat proteins (often bind to cargo receptors)

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24
Q

what controls coat assembly

A

coat recruitment GTPases

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25
what does assembly of coat proteins involve
binding of GTP form
26
what does disassembly of coat proteins involve
GTP is hydrolyzed to GDP
27
which of cytosol and ER membrane bound forms of coat proteins are inactive and active
GDP is in cytosol = inactive GTP is ER membrane-bound = active
28
what allows for specificity in vesicle targeting
surface markers that identify vesicles according to their origin and type of cargo
29
what is recognition of donor vesicles by acceptor membranes controlled by
SNAREs and Rabs
30
what do Rabs do
type of GTPase that works together with other proteins to regulate the initial docking and tethering of the vesicle to the target membrane
31
how do Rabs transfer to SNAREs
Rabs release protein when it is hydrolyzed to GDP - this transfers to SNAREs
32
what do SNAREs do
provide specificity and catalyze vesicular fusion of the target membrane
33
what are v-SNAREs and t-SNAREs
v = vesicle t = target membrane make a very tight interaction and the force of this drives fusion events between membranes - separated later using ATP hydrolysis
34
how do Rab and SNAREs work together
Rab tethering protein catches vesicle, SNAREs force fusion between two membranes
35
how does cargo recruitment work
- membrane proteins have exit signals in the cytosolic tails that are recognized by coat proteins - soluble proteins bind to cargo receptors that have exit signals in their cytosolic tails
36
what happens after transport vesicles bud off of ER
they fuse together to form intermediate compartments called vesicular tubular clusters
37
what do vesicular tubular clusters do
- travel towards the cis golgi via motor proteins on microtubule tracks - generate coated vesicles going back to the ER (COPI coat) - retrograde transport
38
what happens with ER retrieval signals
- membrane ER resident proteins retrieve signals in their cytosolic tails, recognized by COPI coat proteins - soluble ER resident proteins retrieve signals within their structure and bind to receptors
39
what are the two models for how cargo travels through the golgi
static model and dynamic model
40
what is the static model
golgi stacks (cisterae) remain the same throughout - vesicles travel between them, moving proteins
41
what is the dynamic model
golgi stacks (cisternae) move upward, changing their protperties slightly as they migrate
42
how do enzymes get returned
through vesicular transport in retrograde directions
43
how do proteins leaving golgi get to plasma membrane
vesicles carrying them fuse with the plasma membrane via exocytosis
44
what are the two basic pathways of secretion
constitutive secretory pathways and regulated secretory pathway
45
what happens with constitutive secretory pathway
- once you leave golgi, directed to plasma membrane which you fuse with - no additional signal required
46
what happens with the regulated secretory pathway
secreted components are concentrated into secretory vesicle which moves to plasma membrane. it requires an external signal to trigger fusion of vesicle with plasma membrane
47
what are clathrin-coated vesicles used for
transport between plasma membrane, endosomal system, and golgi
48
what is the structure of clathrin
composed of three copies each of heavy and light chains; arranged in a triskelion
49
what does clathrin interact with
cargo receptors and other markers to drive vesicle formation, then clathrin coat is lost
50
what is dynamin
a GTPase that is a cytoplsasmic proteins which control the pinching-off of clathrin-coated vesiclse
51
how does dynamin work
- wraps around the stem of the budding vesicle - brings inner leaflet membranes of vesicles together - fusion of these membranes severs the vesicle from the donor compartment - GTP hydrolysis regulates rate of vesicle pinching off
52
what are the characteristics of lysosomal enzyme cargo
soluble, carry a unique marker - mannose 6-phosphate (M6P) groups
53
what happens when lysosomal enzyme cargo is recognized by M6P receptor in golgi network
it's packaged into clathrin-coated vesicles for delivery to lysosomes
54
what are endosomes
intermediate organelles in vesicular transport pathways between plasma membrane, lysosomes, and golgi
55
what are the three classes of endosomes
early, late recycling
56
what are early endosomes
develop from endocytosis
57
what are late endosomes
mature from early endosomes to become more like lysosome compartments
58
what are recycling endosomes
compartment that after some cargo has delivered to endosomes, compartments can go back to plasma membrane
59
what do endosomes eventually mature into
lysosomes by becoming increasingly acidic because of addition of proton pumps
60
what do proton pumps do
move protons from cytosol and concentrate them inside compartment to become more acidic
61
what happens in exocytosis
vesicle fuses with plasma membrane and releases cargo
62
what happens in endocytosis
vesicle comes in from outside and pinches off
63
what does low pH activate enzymes to do
to be able to degrade biological molecules
64
what are multivesicular bodies
vesicles with vesicles in them - characterizes maturation of late endosomes
65
what happens to membrane proteins and lipids as vesicle cargo
they're removed from the plasma membrane and some will be recycled back to surface, some will be degraded
66
what happens to soluble proteins as vesicle cargo
they're from extracellular space and are carried into the lumen to be degraded
67
what are the common components targeted during exocytosis
cell surface receptors and the ligands that bind them
68
what is phagocytosis
cellular eating - the ingestion of large particles, such as microorganisms or dead cells via vesicles called phagosomes
69
what is pinocytosis
cellular drinking - the ingestion of fluids and solutes by vesicles called pinocytic vesicles, including receptor-mediated endocytosis
70
what do cells do constantly in terms of endocytosis
pinocytosis - doesn't require a trigger - it's how cells get fluids in cell and sample nutrients
71
how does cholesterol get into cells
via receptor-mediated endocytosis
72
what receptors generally get recycled to the cell surface
receptors that involve the transport of nutrients
73
what receptors generally get degraded
receptors involved in signaling events because that turns off signaling to reset the cell
74
what is transcytosis
moving from one side of a polarized epithelium to another

BSCI330 SPRING (24 decks)

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