z
Parti. (20 points total)
Fill-in the blanks. 1 points each blank.
1.
Microtubules
A.
Name the motor protein(s)
B.
Name the coating protein
C.
Name the structure formed when ER-derived vesicles fuse with one another
Minus end
CQPjj.
-v-ransporA
D.
Name the coating protein
2.
Name the signal sequence that distinguishes the import of secretory proteins from
that of membrane proteins into endoplasmic reticulum.
3.
If an autophagosome is formed by engulfment of a mitochondrion by the ER
membrane, how many layers of membrane separate the matrix of the mitochondrion from
the cytosol outside the aothophagosome?
T XNO
^
4.
Name the Golgi enzyme that catalyzes reactions to tag lysosomal proteins in the
Golgi apparatus
5.
Name the core region of a glycoprotein to which N-linked oligosaccharide is
added in ER.
t<++•
A ^wv ,__ V _ ^w_». / c*£»/'
6.
The electron micrograph below shows a neutrophil ingesting a dividing
bacterium. What is the special name for this process?
bacterium
pseudopod
plasma
membrane
7.
Name the cytosolic GTPase that binds to the neck of a clathrin-coated vesicle and
helps it to pinch off from the membrane.
8.
IX
How many polypeptide chains does one clathrin triskelion have?
9.
Name the Ca2+-binding protein that can trigger the contraction of smooth muscle
once there is a Ca2+ influx.
CQ\
10.
Name the organelle of animal cells that is the primary microtubule organizing
center and acts as the spindle pole during mitosis.
11.
Name the electron carriers produced by citric acid cycle.
12.
List three conserved functions of peroxisomes:
r
13.
Name the mitochondrial translocator on the inner membrane that directs proteins
from the mitochondrial matrix to the inner membrane.
14.
At what pH the lysosomal hydrolases have the optimal activity? _ O
15.
Name the electron carrier in the complex I of respiratory chain that generates free
FQVi
oVtde
Part II. (10 points total)
Cirle either True or False. 1 point each question.
1.
Several cellular proteins can bundle intermediate filaments. Filaggrin bundles
keratin filaments in skin whereas plectin bundles vimentin. fTrue) False)
2.
Traw-SNARE complex consists of three v-SNAREs and one t-SNARE that
require ATP to form a twisted parallel four-helical bundle, ffruey False)
3.
The signal peptide, when emerges from the ribosome, binds to a hydrophobic sit
on the ribosome causing a pause in protein synthesis, which resumes when signal
recognition particle binds to the signal peptide. (True /(False}
4.
Ca2+ can freely move in and out of endoplasmic reticulum and nucleus.
However, macromolecules such as proteins require transporters to move in and out of
endoplasmic reticulum and nucleus. /{TruQ / False)
5.
Arf GTPases are responsible for COPI and COPII coat assembly at Golgi
membrane. (Trud^/False).
6.
Quiescent cells
Cells infected with an active GTPase
Cells in the right panel of figure above demonstrate stress fibers because these
cells have been injected with active Rac-GTPase. (Tjruey False)
7.
Ribosomes bound to endoplasmic reticulum are structurally distinct from free
ribosomes in that the ER-boundjihosome has a structural unit called Sec61 which is
missing in the free ribosome. (Tn$/ False)
8.
Although the building block of intermediate filaments is a polar tetramer, the-^
filaments have identical ends after the building blocks are linked together. (True /(False)
> »
9.
To accomplish the docking of appropriate vesicles tpjhe target membrane, Rab
proteins must bind specific complementary Rab proteins, (jru^ / False)
10.
Cytosolic chaperone proteins are required for import of all proteinsjnto
endoplasmic reticulum and mitochondria but not into the nuclei. (True (False) )
•
Part III. (80 points total)
Multiple choice. Circle ALL correct answers (there may be more than one). 2
points each question.
1.
The growth rates at the plus and minus ends of actin filaments as a function of
actin concentration are shown in the figure below.
Rate of filament growth
(molecules per second)
20 —
Actin monomers (u.M)
0
If you add actin filaments of defined length to a solution of actin monomers at the
concentration indicated as A, B, C, D, or E, which concentration of the solution will let
you control the growth of actin filaments at the plus end but not the minus end?
A.
Concentration at A or B
B.
Concentration at B or C
1ibn at
2.
Which of the following favors the destruction of misfolded ER proteins that
escape to the cytosol?
A.
Action by ER N-glycanase and multiubiquitylation
B.
Action by ER mannosidase and polyubiquitylation
~_ Action by cytosolic N-glycanase and polyubiquitylation
D.
Action by ER mannosidase and multiubiquitylation
3.
How would cytochalasin and phalloidin affect actin filaments?
A. , Cytochalasin increases the filament length whereas phalloidin facilitates
_ the depolymerization.
B.
Phalloidin increases filament length whereas cytochalasin facilitates the
depolymerization.
Both cytochalasin and phalloidin increase the filament length.
Both cytochalasin and phalloidin facilitate the depolymerization.
—--•—— -- —____
•_
___
2
4.
How do you describe Sail GTPgseS-switches'between
a GTP-bound soluble form and a GDP-bounc
•* »
membrane-anchored form.
directly binds the cargo receptors on ER membrane.
C.
It binds clathrin in vesicles forming from the ER membrane.
D.
It binds a GTPase exchange factor on Golgi membrane.
-a
5.
C.
D.
jes NSF do during vesicle transport?
It facilitates the binding between the clathrin coat and transmembrane
proteins, includjng,transmembrane cargo receptors.
_
:afalyzes the disassembly of the helical domains of paired SNARE
proteins.
It catalyzes the binding between Sari GTPase and a coating proteirn.
It catalyzes the membrane fusion of two vesicles.
6.
The 0-glycosylation of a glycoprotein takes place in Golgi by adding sugar
residues to a core protein. Which of the following is usually added first?
A.
N-acetylglucosamine
B. . N-acetylgalactosamine
~Xylose-galactose-galactose-glucuronic acid
7.
What is the difference between high mannose and complex mannose
oligosaccharides?
High mannose oligosaccharides are attached to a glycoprotein in ER j
whereas complex mannose pligosaccharides are aU^chedjisJ^Qlg^f-^
igh raannose oligosaccharides are generated after trimming of complex
mannose oligosaccharides and addition of mannose residues to the newly
trimmed complex mannose oligosaccharides.
Complex mannose oligosaccharides are generated after trimming of high
C.
mannose oligosaccharides and addition of other sugar residues to high
mannose oligosaccharides.
High mannose oligosaccharides do not have glucose whereas complex
D.
mannose oligosaccharides consist of glucose.
8.
Which of the following correctly describe events in endocytosis?
A.
All endocytosed macromolecules that enter early endosomes are delivered
;e endosomes and lysosomes for degradation. ...
Many endocytosed macromolecules that enter early endosomes recycle
from early endosomes back to the plasma membrane without going .
through late endosomes and lysosomes.
ome endocytosed macromolecules that are released from transport
vesicles budding off from the plasma membrane recycle back to plasma
membrane without going through early endosomes, late endosomes, and
lysosomes.
D.
Coated pits on the apical surface of an epithelial cell will pinch off and
fuse with the plasma membrane on the basolateral surface. In that way,
macromolecules are transported across the eoithelium.
y.
vynicn 01 me loiiowmg descnbes caveolae?
The invaginated structure that forms from clathrin-coated lipid rafts at the
cell surface and buds off internally to form a pinocytotic vesicle.
"TllC iiivctgmated-stmetui'c that fuiins flWli lipid ratts^t the cell surface and
buds off internally by caveolin to form a pinocytotic vesicle.
The invaginated structure that forms from lipid rafts at the cell surface
coated and provides SV40 virus an entry site to infect the cell.
D.
A plasma membrane structure that does not require either coating proteins
or a cytosolic GTPase to deliver materials into the cell.
1 0.
How does ER make sure a protein is properly folded before being released? are
incompletely folded ^proteins retained in ER until they are properly folded?
Mannose residues of N-linked oligosaccharides serve as a marker of
protein folding status. Calreticulin or calnexin binds to the exposed
Glucosyl transferase keeps a terminal glucose residue on the N-linked
oligosaccharides of incompletely folded proteins. Calreticulin or calnexin
binds to the terminal glucose on the N-linked oligosaccharides to retain
C.
D.
11 .
x
Glucosidase trims away all glucose residues from N-linked
oligosaccharides of incompletely folded proteins in ER. Calreticulin or
calnexin recognizes these incompletely folded proteins because these
proteins lack glucoses on N-linked oligosaccharides.
Completely folded proteins do not have N-linked oligosaccharides from
ER. Incompletely folded proteins have N-linked oligosaccharides that
serve as markers to be retained in ER by Calreticulin or calnexin.
of the following is an example of receptor mediated_endoc_yjosis?
Low-density lipoproteins (LDL) on cell surface bind extracellular
r itg inlprnaliVatinn iritn the cell.
Receptor for LDL on cell surface binds extracellular LDL for the
internalization of LDL.
Many cholesterol form large complex with LDL in blood in order to be
internalized into the cell.
The membrane of HIV virus fuses with the membrane of the host cell and
the content of HIV virus is internalized into the cell.
12.
How do you describe the multivesicular body?
All endocytosed materials in a multivesicular body are tagged with monoor multi-ubiquitin.
It is a vesicle that sorts out internalized materials for either apical or
basolateral surface of an epithelial cell.
C.
It contains internal vesicles where all endocytosed molecules in early
dosomes get degraded.
D.
Endocytosed membrane proteins tagged with mono- or multi-ubiquititt at
their cytosolic domains aie sorted into trie internal vesicles of the
multivesicular bodv.
13.
Which of the following is occurs to kinesin I movement cycle on microtubules in
the hand-over-hand model?
A.
Replacement of ADP-bound leading motor head of kinesin I with ATP
v triggers .the detachment of kinesin I from microtubules.
f
E.
ATP hydrolysis both leading and lagging motor heads of kinesin Iare~\
- followed by kinesin I detachment and power stroke on microtubules_>^x
C.
ATP hydrolysis of the lagging motor head of kinesin I triggers the
repositioning of the lagging motor heads and ATP-binding of the leading
lotor head of kinesin I.
ATP hydroTysis ot trie leading motor head of kinesin I triggers"the
repositioning of the leading motor heads and ATP-binding of the lagging
motor head of kinesin I.
• » » — . - , , „ . ...A-
-
Hll
-
_1|_-_ L
;----
._....
'-
'
14.
How do misfolded proteins in ER trigger synthesis of additional ER chaperones?
A.
Misfolded proteins in the ER activate a transmembrane kinase in ER,
which activats its own endoribonuclease domain, causing it to remove an
intron from a specific mRNA to form a "spliced mRNA". This new
mRNA encodes a gene regulatory protein that enters nucleus and activates
the gene for an ER chaperone protein. This chaperone enters the ER and
\ _ai4sjn_thg correct folding of misfolded proteins.
—,^__^
Tvfisfolded proteins in the ER activate a transmembrane kinase in ER,
which recruits an endoribonuclease protein, causing it to enter the nucleus,
This endoribonuclease protein activates the gene for an ER chaperone
protein. This chaperone enters the ER and aids in the correct folding of
bided proteins.
C.
Misfolded proteins in the ER activate a transmembrane kinase in ER,
which activats its own endoribonuclease domain, causing it to remove an
intron from a specific mRNA to form a "spliced mRNA". This new
mRNA encodes a chaperone that enters the ER and aids in the correct
folding of misfolded proteins.
D.
Misfolded proteins escaping from the ER activate a cytosolic kinase which
activats its own endoribonuclease domain, causing it to remove an intron
from a specific mRNA to form a "spliced mRNA". This new mRNA
encodes a gene regulatory protein that enters nucleus and activates the
gene for an ER chaperone protein. This chaperone aids in the correct
folding of misfolded proteins in the cytosol.
15.
ER?
What is the role of chaperone proteins in co-translational import of proteins into
A.
B.
Chaperone proteins are required for the unfolding of signal sequence to be
recognized by SRP.
Chaperone proteins are required for the unfolding of the newly
.synthesized peptide to be imported into ER^
Chaperone proteins are present in the translocator during co-translation;import of proteins into ER.
Chaperone proteins aic nut required loTmlF<^-iransTatTonal import or
proteins into ER.
16.
What are lamellipodia?.; r
A.
RhoGTPases.
B.
Large bundles of actin filaments.
C. ^Membjarie43iQtrusk>ns full ofLdisorganized membrane blebs.
(^\
Membrane structure supported by
17.
How are soluble proteins in ER selectively recruited into vesicles destined for the
Golgi?
A.
Soluble ER proteins have exit signal sequence that direct them to bind the
vesicle coating proteins.
B.
Soluble ER proteins can bind a chaperon protein in the ER lumen. The
chaperone protein binds the vesicle coating proteins.
Soluble ER proteins can be recruited by active Rab GTPases into transpon
C.
vesicles.
————D.
Soluble ER proteins bind membrane receptors. The cytosolic domains of
these receptors bind the vesicle coating proteins.
18.
Which of jhe following describes cytochrome oxidase complex?
An electron-driven pump in the respiratory chain that accepts electrons
from cytochrome c.
B.
An electron-driven pump in the respiratory chain that consists of ironsulfur centers.
C.
An electron-driven pump in the respiratory chain that accepts electrons
from flavin mononucleotide.
D.
An electron-driven pump in the respiratory chain that accepts electrons
from succinate.
19.
How_do you describe the KDEL receptor?
with KEDL sequence in ER. N,
ffiat hindc
B.
A receptor in Golgi that sorts out proteins with KDEL for glycosylation.
A receptor that binds ER proteins with KDEL sequence in Golgi only.
D.
A receptor in Golgi that retains proteins with KDEL sequence in Golgi.
is*
20.
21.
Whichjyp-e-of"vesieles-might carry hormones for secretion from Golgi?
s^fC~
COP T-rmfpiH vpiirlp« •-.
clathrin-coated vesicles.
C.
COP II-coated vesicles.
M6P receptor-enriched vesicles
D.
Phosphoinositides (PIPs) are important molecules in vesicular transport. Why so?
PIPs bind clathrin coating proteins to make the coats more stable on the
vesicles.
B.
Golgi has one particular PIP type. ER has another type of PIP. Therefore,
different coating proteins can bind Golgi membrane or ER membrane by
binding
different PIPs.
_
c
Different membrane domains on the same organelle could have different
types of PjPsfbr the coating proteins to bindL,,.
0!
PI(4,5)P2faciHtates; meTnridTrig of dynamin to the lipid bilaver.
22.
Which of the following proteins facilitates vesicle tethering and docking once it i
bound by an activated Rab GTPase?
SarLprotein
Rab-GEF_
A complementary Rab GTPase
D
Rab effector
23.
Which of the following will result in oxidative stress?
A.
The products generated from reactions catalyzed by catalases can not be
led by reactions catalyzed by peroxisomal oxidases.
The products generated from reactions catalyzed by peroxisomal oxidases
can not be consumed by reactions catalyzed by catalases.
C.
The enzymatic activities ot superbxide dismutases and catalasess are both
increased.
D.
The enzymatic activities of superoxide dismutases and catalases are both
decreased.
24.
How is contraction of skeletal muscle regulated?
AT
Extracellular Ca+ entering a skeletal muscle cell through channels in Ttubules binds troponin C, triggering rapid muscle contraction.
B.
Ca2+ released from the sarcoplasmic reticulum after the entering of
extracellular Ca2+ strengthens the binding of troponin I to the actin
filament, triggering rapid muscle contraction.
JC.
Extracellular Ca+ entering a skeletal muscle cell through channels in Ttubules binds tropomyosin, triggering rapid muscle contraction.
Ca2+ released from the sarcoplasmic reticulum after the entering of
extracellular Ca2+ binds troponin C, triggering rapid muscle contraction.
25.
What is chemiosmotic coupling?
A.
Electron transport chain that receives high energy electrons from the citric
acid cycle and generate the proton gradient across the inner mitochondrial
membrane that is used to power ATP synthesis.
General term for a series of electron carrier molecules along which
electrons move from a higher to a lower energy level, and ultimately to a
final acceptor molecule,
etabolic pathway that oxidizes acetyl group to CO2.
Mechanism by which a pH gradient across a membrane is used to drive an
energy-requiring process, such as ATP production.
26.
Actin monomers are present in cells at a concentration higher than the critical
concentration measured in pure actin solution. What is your explanation?
A.
Gelsolin slows down the rate of actin polymerization in cells by severing
so that actin filaments can not take up more actin monomers.
B.
Cofilin stabilizes new actin filaments in cells so that they can not take up
more actin monomers.
C.^ Profilm binds aciiu monomers to prevent them from polymerizing.
D.
Thymosin binds actin monomers to prevent them from polymerizing.
27.
What do you know about mannose 6-phosphate receptor?
It binds proteins tagged with mannose 6-phosphate in cis-Golgi and
transport it through trans-Golgi to lysosomes.
It binds proteins tagged with mannose 0-pnospnate in trans-Golgi where
pH is low, releases the protein cargo in late endosomes where pH is
igher, and comes back to the Golgi.
C.
It binds mannose 6-phosphate in a protein in neutral pH and dissociates
from it in acidic pH.
.
S
It binds mannose 6-phosphate in a protein in Golgi to retain these protein:
in Golgi.
~BL
it
28.
Which of the following will favor the shrinking of a microtubule molecule during
dynamic instability?
(5l'F::c^nTaifiMigJiibttli«-subiinlls are addecTquickly enough to cover the"
GDP-containing tubulin subunits at the microtubule end, resulting in thj
formation of a new GTP cap.
Concentration of freelurJulm'subunits in solution is increased and the rate
of GTP hydrolysis in decreased.
GDP is the only nucleotide present in the solution.
The solution contains a GTP analog that could not be hydrolyzed.
29.
- np^fcr^EAa
How do you describe retrosome?
A.
It coats vesicles moving away from the trans-Golgi to secretory vesicles.
E.
It coats vesicles that carry a lysosomal protein from plasma membrane to
the trans-Golgi.
C.
It coats vesicles that carry a Golgi protein from an endosome back to the
Golgi.
__
/^—
i.g
—
"*~.—
. _ _ ___
L I.IIt coats vesicles that carry an ER protein from^Golgi back t°
30.
iWhich of the following statements correctly describes cell migration?
sj&r~ ^During protrusion, cells extend lamellipodia that are supported by large
C /bundles of actin micro filaments and Rho-GTPase.
During piutmsion, Rac-GTPase triggers a membrane structure at the
moving front.
During traction, phosphorylation of myosin light chains is decreased.
During traction, cofilin decreases the size of actin filament bundles.
:
y
31.
What is axoneme?
A.
Long, highly organized bundles of micro tubules, micro filaments, and
neurofilaments that form the core of a cilium in a eukaryotic cell.
Bundles of microtubules and other proteins that form the core of a ciliunf
in a eukaryotic cell.
__
Flattened, two-dimensional protrusion of membrane supported by a
meshwork of microtubules and kinesins.
D.
Long, hairlike protrusions from the surface of a eukaryotic cell that consist
of microtubules and cvtuulasmic dvneins.
C
32.
If you treat cells with a drug colchicines, which of the following will happen to
the cells?
Jf.
Microtubule stability will be enhanced.
B.
Cell shape will change but the intracellular location of organelles will nol
be disrupted.
C.
The intracellular location of organelles will be disrupted but cell shape
Microtubulewill be disrupted^)
33 .
Which of the following statements is correct about mitochondria! translocators?
A.
Regardless of their final destination in the mitochondria, all proteinsTlikt
are
synthesized
in the cvtosol must first enter TOM
complex.
^^
mi
~~~^^^^""
•• •
*•..
Import of all inner membrane proteins in mitochondria must first enter
TIM23.
15^ £1 ^
C.
Import of all outer membrane proteins in mitochondria must first enter
OXA.
D.
Import of all matrix proteins in mitochondria must first enter Sam.
34.
Place the following in order of size,
A.
Protofilament. »
( 2.
B.
Microtubule.'
( 3
C.
Tubulin dimer. \ ( \
D.
Mitotic spindle. M ( 4
L
from the smallest to the largest (1 to 4)
)
)
)
)
35.
How do you describe the distinct features of the y-tubulin ring complex and ARP
complexZ
The y-tubulin ring complex nucleates microtubule growth by binding at
the minus end whereas the ARP complex nucleates microfilament growth
hv hinHing -at the plus gr^f
j6;
The y-tubulin ring complex nucleates microtubule growth near the plama
membrane whereas the ARP complex nucleates microfilament growth
deep inside the cell.
Both the y-tubulin ring complex and the ARP complex can bind the side of
the microfilaments to build a web-like branching network.
Both the y-tubulin ring complex and the ARP complex nucleate the
cytoskeletal filaments by binding at the minus end and are evolutionally
related to the subunits of the filaments they nucleate.
36.
Which of the following
ng correctly describes the structural feature of skeletal
muscle cell?
here are lots of nuclei and sarcoplasmic reticulum in a skeletal
cell.
"sarcomere has one pair each of Z discs, tropomodulins, CapZ's, and
myosins.
There is equal number of myofibrils and transverse tubules.
I3C
Skeletal muscle cells do not have plasma membrane.
37.
Which of the following does not describe the cytoskeleton influence on cell
behavior?
The moving front of a migrating cell requires branching of actin
micro filaments mediated by Arp and cofilin.
Vesicle transport motored by dyneins but not kinesins occurs during the
formation ofaxonJiQni the neuronal body.
Epidermal blistering diseases result from the malfunction of intermediate)
filaments.
Jvfrcrottttrales carTget Golgi or mitochondria moving about within the cell.
38.
Katanin is activated during mitosis. What do you suppose the role of katanin in
mitosis?
^1^ It generates shorter microtubules with GDP-tubulin at the exposed ends/
B. , It caps the ends of newly polymerized microtubules.
C.
It stabilizes the minus ends of microtubules.
"~TX
It cross-links the microtubules.
"/^Jj
39.
mil f a n !•••"
1
'•
H "••"••-*•-••«»-
*
c
—
*
i
i
i
--
The influence of stathmin on microtubule structure is due to
A.
the shrinking pool of the tubulin dimers
the increased pool of the tubulin dimers
C.
the inability for stathmin to bind microtubules
the inability for stathmin to bind tubulin dimers
40.
Which of the following is not necessary for a lysosomal protein to be sorted out in
Golgi?
'
_^
1
-C. / N-acetylglucosamine
Mannose on a glycoprotein