Final Exam Flashcards
All COPII vesicles interact with ____
Sec24
some intergral ER membrane proteins are targeted to _____ vesicles for transport to ____
COPII, Golgi
certain intergral ER membrane proteins also bind ___ proteins in the ____
cargo proteins, lumen
Microtubules act as “____ ____” for large aggregates of transport vesicles
railroad tracks
COPI vesicles have ___grade trasnport and transport from ___-____ to ______
retrograde transport; from cis-Golgi to rough ER
ER-resident proteins may assist in what?
folding and modification on newly synthesized secretory proteins
most ER-resident proteins contain ____ sorting sequene
KDEL
KDEL sorting sequence is located at the _-terminus
C-terminus
where do ER-resident proteins bind
to complex of COPI vesicles
The Di arganine sequence can also target what?
certain proteins to COPI vesicles
what is cisternal maturation
like an assembly line, proteins move in sequence through the compartments which each house different enzymes
cisternal maturation is responsible for ____grade transport
anterograde
anterograde trainsport is from __ - ___ golgi
cis tor trans Golgi
cis-Golgi protein ____ is fused to ___
Crg4, GFP
trans-Golgi protein ___ is fused to ___
Sec7, DsRed
Resting membrane potential depends largely on flow of what
K+ ions
What is the usual resting membrane potential
60-70 mV
simple diffusion rate is proportional to what
concentration gradient, hydrophobicity and size
post translational translocation ATP hydrolysis is required by what
BiP
Hsp70 has a similar function to what
BiP
Wht are adaptor protein complexes
determines which cargo proteins are in a vescile by binding cytosolic domains of membrane proteins
what are the cytoplasmic sorting signals in COPI vesicles
KKXX and di-arganine
what is the protein that assebles and disassembles COPI coat
ARF
What is the AP3 complex
vesicles that bud from trans-Golgi en route directly to the lysosome
T or F:the AP3 complex uses the ARF protein
T
What do clathrin coated vesicles do
AP1-vesicles that bud from trans-Glgi en route to late endosome
What does GGA do
buds from trans-golgi network to late endosome
What does AP2 do
buds from plasma membrane during endocytosis
What is the Sorting signal in clathrin coated vesicles
YXXo
What are the five destinations of Adaptor protein complexes
COPI vesicles, AP3 complex vesicles, Clathrin coated vesicles, constitutive secretory vesicles and regulated secretory vesicles
___ pinches off clathrin coated vesicles
dynamin
what do constitutive secretory vesicles do
transport secreted protein and plasma membrane proteins to plasma membrane
what do regulated secretory vesicles do
store and process secreted protein until signaled to fuse with the plasma membrane to secrete proteins
What are the two domains of polarized epithelial cells
Apical and basolateral
What is between apuical and basolateral membranes to prevent povement
tight junctions
how are apical and basolatreal bound membrane proteins sorted
initally transported together in trans-golgi network by COPII and cisternal maturation, sorted into transport vesicles with v-SNAREs and Rab proteins
Influenza glycoprotein only found on ___ membrane
apical
VSV G protein only found on ____ membrane
basolateral
what helps membrane proteins associate with clatharin adapter proteins
Tyrosine and di-leucin based motifs
proteins targeted to apical membrane often have ___ membrane anchor
GPI
what is transcytosis
apical proteins move in vesicles across the cell and fuse to apical membrane
what visualizes protein size and abundacne
SDS-PAGE
what is the ionic detergent in SDS PAGE
SDS
what is receptor mediated endocytosis
small vesicles invaginate from plasma membrane
what are the four types of lipoporteins
chylomicrons, VLDL, LDL and HDL
What do chylomicrons do
transport triglycerides from the diet
What do VLDLs do
transport triglycerides made by liver, cells remove triglycerides becoming LDL
What do LDLs do
less healthy, deliver cholesterol to tissues
what do HDLs do
return excess cholesterol from tissues back to liver
Receptors contain ______ taht target them for endocytosis
sorting signals
LDL receptors release ___ at low pH
apoB-100
HIgh plasma LDL leads to ___
disease
What is the transferrin receptor complex
functions to deliver iron to cells
waht is apotransferrin
no iron bound
what is ferotransferrin
full transferrin, two Fe3+ bound
waht is the transferrin receptor
binds ferrotransferrin and initiates endocytosis
what do lysosomes do
degrade extracellular materials taken up by the cell
Where do normal transport vesicles bud
outward from organelle membrane to the cytosol
where do internal vesicles bud
inward from endosomal membrane to the lumen
most cargo protein destined to enter a multi vesicular endosome are tagged with what?
a single ubiquitin molecule
Retroviruses required ______ complexes to bud from plasma membrane
ESCRT
What is the purpose of autophagy
serves to recycle macro molecules to serve as nutrients under stressful conditions
how does autophagy work
envelopes a region of cytoplasm or organelle into double membarne for delivery to lysososme
What is the most important key to supporting the needs of the cell
the cytoskeleton
What are the three components of the cytolskeleton
microfilaments, microtubules and intermediate filaments
how is the cytoskeleton function regulated
cells sense extracellular signals and interpret them to direct arragement of the cytoskeleton
What happens to the cytoskeleton in the abscence of extracellular signals
the cells do not become polarized, but the cytoskeleton stillforms
What is the building block of microfilaments
actin
T or F: microfilaments have reverible assembly
T
What is actin
it is an abundant intracellular protein in eukaryotic cells
What are the three different groups of actin
alpha beta an y actin
What is alpha actin
for contractile sturctures
waht is beta actin
cell cortex and leading edge of motile cells
what is y actin
is on stress fibers
Each actin molecule contains a ____ ion
Mg 2+
What are the two forms of Actin
G-actin and F-actin
Actin is a _____ase
ATPase
What is G-actin
monomer separated by 2 lobes by a deep cleft, ATPase fold is the site of ATP and Mg binding, denatures quickly. addition of cations induces filament formation
what is F-actin
subunits in actin fillaments arranged in helical strands wound around each other, ATP binding clefts all oriented towards - end. Each subunit contacts one above and one below
The + end of microfilaments is favoured for the addion of what
actin subunits
The - end of microfilaments is favoured for what
unit in disocciation; ATP binding cleft exposed to surrounding solution
Where on the microfilament does Myosin attach
to the sides of microfilaments with a slight tilt
T or F: actin binding proteins contribute to staiblity
T
T or F: G-actin can be purified at low concentration
F: high
what are the three steps in actin polymerization
Nucleation phase, Elongation phase and Steady State phase
Filaments grow __x faster at + end than - end
10x
When ATP-G-actin binds to the + end, what happens
ATP is hydrolyzed to ADP and Pi
What are the three actin binding proteins
Profilin, cofilin and Tymosin-B4
What des profilin do
helps nucleotide exchange so ATP actin is ready for the (+) end
What does cofilin do
Specifically binds ADP-F-actin, fragemnts ADP-actin filament regions, enhancing depolymerization
What does Thymosin-B4 do
provides a buffered reservoir of ATP-G_actin for polymerization
What are the two capping proteins
CapZ and Tropomodulin
what does CapZ do
blcoks assembly and disassebly, caps (+) end
Waht does Tropomodulin do
binds (-) end, inhibits assembly and disassebly
actin nucleating proteins are conducted by which two signal transduction pathways
Formin and Arp2/3 complex
how is formin regulated
RBD binds to Rho-GTP, exposing FH2 to nucleate new filament, FH1 domain recruits profilin-ATP-G-actin
in active site is where FH2 domain inhbitied
what is the Arp2/3 complex
seven subunites that nucleate assembly of branced actin, bust me activated by NPF
Filaments grow at their (+) end until what?
capped by CapZ
certain toxins affect actin by promoting ______ or ______ of filaments
depolymerization and polymerization
What is needed to form filaments into bundles or networks
actin cross-linking proteins
What is myosin?
actin-based motor protein
what do mysoins do
move along actin filaments and convert energy from ATP hydrolysis to do work
To or F: different myosins perform different functions
T
what are the three types of Myosin
Myosin II, I and V
what is myosin II
protein complex of six polypeptide subunits; 2 heavy chains and 2 light chains
what is myosin I
one single headed myosin, encoded by eight different human myosin genes
what is myosin V
two head domains and six light chains per neck. encoded by three different myosin genes
what do myosins use for coupling ATP hydrolysis
cross-bridge cycle
how many profilaments in a microtubule
13
what is the major protein in microtubules
tubulin
what happens to GTP in alpha tubulin
is trapped and never hydrolyzed or released, exposed at - end
what happens to GTP in beta tubulin
can be hydrolyzed to GDP and exchanged for free GTP, exposed at + end
alpha tubulin contacts with alpha tubulin of neighbouring except at the _____
seam
microtubules are assembled from specific sites called
mixeorubule organizing centers (MTOCs)
Generally, the __ end stays anchored to the TMOC while the __ end stays away from it
-, +
what is the main MTOC of animal cells
Centrosome
waht is the main MTOC for cilia and flagella
Basal body
what is the structure of a singlet centrosome
nine linked triplet microtubules
what forms the template for the (-) end
Y-tubulin ring complex
dyanimc instabliity depends on the presence or absence of what
GTP-B-Tubulin cap
disassembly pauses when?
GTP-B-Tubulin is found on the microtubule and starts assembly phase
what is the difference between GTP-B-tubulin cap and GDP-B-tubulin cap
GTP promotes assebly while GDP promotes disassembly
There is assembly to disassembly when GTP hydrolysis rate __ GTP tubulin action
>
There is disassembly to assembly when GTP hydrolysis rate __ GTP tubulin action
what may stabilize or destabilize microtubules
mirotubule-assocated proteins (MAPs)
Spacing reflects difference between the lenghts of the ___ and ___ projection domains
MAP and tau
what do (+) end-binding MAPs do
enhance plymerixation at (+) end, reduce frequency of catastrophes link microtubules to other cell structures
What is the Kinesin-13 family
bind and curve the + end of profimalents into GDP-B-tubulin, require ATP for hydrolysis
when kinesin binds to dimers, what happens?
it curves them so curvature is that of disassembly
T or F: organelles move along microtubules in either direction
T
What are the microtubule based motor proteins
Kinesin and Dynein
how do kinesin and dynein move along microtubules
using ATP hydrolysis
What is Kinesin 1
tail doamin binds to receptors on cargo, head domain binds microtubules and ATP
T or F: kinesin 1 always tansports vesicles from (-) end to (+) end of a microtubule
T
what happens in the inhibited form
had folds back and interacts with tail, inhibits ATPase activity
how is kinesin-1 regulated
motor binding to vesicle receptor unfolds kinesin activating ATPase actity
transports cargo toward + end
T or F:there is convergent evolution between mysoin and kinesin
T
dynein transports organellees towards the (_) end
-
how many AAA ATPase domains in the dynein head
six
what is the dynactin complex
cytpoplasmic dynein cant bind to cargo on its own, so uses dynein complex to link dynein to cargo
dynactin complex contain what
one actin subunit and capZ at + end
the direction of organelle transport is determined by the _____
motor protein
Retrograde transport of late endosome is by __________
cytoplasmic dynein
Anterograde transport of seceretory vesicle by ______
kinesin
