CELL BIOLOGY - BIOL 303
EXAM 1
There is only 1 correct answer per question. There are a total of 35 questions. All questions are
of equal weight and there is no partial credit.
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YOU ANSWER !
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1.
Which of the following statements is not part of the cell theory?
a.
b.
C.
d.
e.
2.
Which of the following statements about cells are not true?
a.
b.
C.
d.
e.
3.
7580% of cells by weight is water, inorganic ions, or small organics
The most abundant macromolecules in cells are proteins
Evolution has generated tremendous diversity, however, much of the cellular
biochemistry and architecture is constant among organisms
Archaea are like eukaxyotes in that they have a nuclear membrane, however, their DNA
sequence is more closely related to prokaryotes
A cell is the smallest unit of life that can survive autonomously and replicate
The membrane
::
C.
d.
e.
4.
All cells replicate their DNA at least once every 24 hours
Cells can arise only by division from a pre-existing cell
All cells contain a plasma membrane, a nucleus delimited by a nuclear membrane,
mitochondria, lysosomes, Golgi, plus other organelles
The cell is the structural unit of life
Two of the above.
Surrounding the nucleus of eukaxyotic cells consists of two lipid bilayers
Of the rough endoplasmic reticulum is the site of fatty acid and phospholipid biosynthesis
Of the Golgi complex includes the cis, medial, and trans regions, all of which are studded
with ribosomes
Surrounding mitochondria contains enzymes that converts startch to oxygen and glucose
Two of the above
A major difference between prokaryotic and eukaryotic cells is
FL
C.
d.
e.
Prokaryotic cells use RNA as their genetic material, while eukaryotic cells use DNA
Eukaryotic cells respond to external stimuli, while prokaryotic cells do not
All prokaryotes contain an additional outer membrane and pexiplasmic space between
their outer membrane and cell wall, while eukaryotic cells only contain a cell membrane
Nucleic acid replication in prokaryotes proceeds via a very different process than nucleic
acid replication in eukaryotes
None of the above
2
5.
A protein synthesized by a eukaryotic cell
a.
b.
ii:
e.
6.
Bacterial chromosomes
;:
:.
e.
7.
i:
e.
Metaphase chromosomes contain histone proteins
Metaphase chromosomes contain non-h&one proteins
Metaphase chromosomes are less condensed than interphase chromosomes
Metaphase chromosomes contain a protein scaffold
Metaphase chromosomes are only found in eukaryotic cells
In eukaryotic cells
E:
;:
e.
9.
Differ from eukaryotic chromosomes because they are circular
Usually encode monocistronic mRNAs
Have at least 4 ori’s per chromosomes when replicating
Usually contain one ribosome binding site for each structural gene
Two of the above
All of the following statements are true about metaphase chromosomes except:
;:
a.
Is dumped into the lumen of the Golgi where it is cleaved from the tibosome to which it
is attached
May contain a signal sequence that targets it to different endpoints, such as the plasma
membrane, lysozome, or other cellular locations.
Is translated on the smooth endoplasmic reticulum if it is destined to be secreted.
Usually travels to the nucleus before export from the cell
Two of the above
There are multiple ribosome binding sites per mRNA
Transcripts are polycistronic
Only approximately 5% of the DNA is coding/regulatory
There are no repeated DNA sequences
Two of the above
Which of the following statements is r& true for eukaryotic cells:
a.
b.
C.
d.
The complexity of the organism does not correlate with the amount of DNA per haploid
genome
Genes can be present in families, which are groups of genes that are related by sequence
Several types of repeated DNA sequences are present, including tandem repeats of short
sequences of non-coding DNA, 100’s of identical copies of certain coding sequences, and
duplicated copies of coding sequences
Techniques such as FISH are useless to distinguish the DNA of one individual from
aXlOthC!r
e.
Two of the above
10.
Eukaryotic nuclear DNA
a.
b.
C.
d.
e.
11.
RNA that is exported from the nucleus to the cytoplasm
it:
C.
d.
e.
12.
Is bound to hnRNA proteins via a specific amino acid motif
Must be capped at its 3’ end before export
Has a specific sequence of 6 nucleotides 5’ to the position where the poly A is
governs polyadenylation
Contains both introns and exons
None of the above
added that
Researchers demonstrated that mature mRNA is exported from the nucleus to the cytoplasm and
can shuttle in and out of the nucleus via nuclear pores by
a.
b.
C.
d.
e.
13.
When extracted under low salt conditions consists of nucleosomes, which look like
beads on a string
When extracted at physiological salt conditions consists of nucleosomes, which look like
be& on a string
Is compressed into the nucleus because of the binding of acidic histone proteins to the
positively charged DNA
If’ fully extended is much shorter than the diameter of the cells from which it is taken
Two of the above
Microinjecting individual, small gold particles into the cytoplasm and watching them
enter the nucleus
Microinjecting individual, small gold particles into the nucleus and watching them travel
to the cytoplasm
Fusing Xenopus oocyte cells with HeLa cells and staining the resulting heterokaryons
with antibodies and fluorescent probes specific for proteins localized to the HeLa cell
nuclei
Watching newly synthesized proteins move from a HeLa cell nucleus to a Xenopus
oocyte nucleus in Xenopus X HeLa cell heterokaryons.
Two of the above
The nuclear localization signals governing trafficking of proteins into the nucleus
a.
b.
C.
d.
e.
Were identified using mutants of SV40 virus in which the SV40 T antigen did not
localize to the nucleus
Were identified using fusion proteins consisting of parts of cytosolic proteins that do not
localize to the nucleus and parts of proteins that do localize to the nucleus
Were identified using electron microscopy techniques
Are very long peptides >l 50 amino acids in length
Two of the above
4
14.
The human immunodeficiency virus (HIV)
Z:
;:
e.
15.
According to the current model for protein extort from the nucleus to the cytoplasm
;:
i:
e.
16.
Ii:
e.
Eukaryotic cells contain linear chromosomes
Eukaryotic cells have more than one chromosome
Eukaryotic cells contain a nucleus
Eukaryotic cells contain more forms of DNA polymerase
None of the above
In the Meselson and Stahl experiment in which DNA replication was studied
a.
b.
::
e.
18.
Hydrolysis of GTP is not required
A cyclical reaction occurs in which the cargo is carried through the nuclear pores by
exponin + GTP + a GTPase
Export is a passive process
The cargo is released from exportin in the nucleus when GTP is hydrolyzed to GDP
None of the above
Special structures called telomeres are needed in eukaryotic cells but not bacteria because
a.
b.
17.
Over rides the rule that only t%lly spliced mRNAs exit the nucleus
Contains a protein, called Rev, the binds to cytoplasmic proteins and enables them to
traflic into the nucleus in infected ceils
Transcribes separate mRNAs for each of its proteins
Transcribes a single transcript that cannot exit the nucleus because it is not fully spliced
Two of the above
Bacteria were grown in medium supplemented with gold particles so that RNA densities
could be measured
DNA banding patterns were consistent with the conservative model of DNA replication
DNA banded in density gradients based on its content of A’s, T’s, G’s, and C’s
DNA banding patterns were consistent with the semi-conservative model of DNA
replication
Two of the above
DNA replication in eukaryotic cells
ba:
C.
d.
e.
Was shown by fiber autoradiography to be unidirectional
Occurs from a single growing fork per chromosome
Starts at an origin of replication which is an AT rich area and has a low melting point
Does not require proteins other than DNA polymerase I
None of the above
19.
During DNA replication in eukaryotic cells
C.
d.
e.
20.
A eukaryotic cell that has the telomerase enzyme
::
C.
d.
e.
21.
d.
e.
location of specific proteins
concentration of Ca* ions in specific regions of the cell
amount of DNA in a cell
volume of a cell
number of organelles in a cell
Deconvolution microscopy is effective because it
FL
C.
d.
e.
23.
Should die earlier than a cell that does not have the telomerase enzyme
Could be a cancer cell, however, experiments with transgenic mice indicate that
telomerase is not necessary for malignancy
Can add a DNA template to the 3’ end of the replicating DNA strand and therefore
completely replicate the chromosome
Faithfully elongates the leading DNA strand
Two of the above
The fluorescent properties of dyes such as fUra- can provide information on the
C.
22.
The lagging strand grows in the opposite direction of the movement of the growing fork
DNA poiymerase joins the small fragments together
A primase erqme makes a DNA primer for each of the small fragments
The leading strand and the lagging Okazaki fragments are elongated from their 3’ end
Two of the above
uses pinholes and a laser to eliminate out of focus fluorescence
uses a point spread function to calculate the focal plane from which each pixel of light
comes and thus eliminates out of focus fluorescence
makes use of the fact that the wavelength of emitted radiation decrease as the speed of
electrons increase to improve resolution
uses polarized light to enhance the contrast of cellular organelles
it alters the phase of light passing through different density components of the ceil
Which of the following will improve resolution of objects under the microscope?
;:
2
e.
decreasing the refractive index of the medium that the sample is in
decreasing the wave length of light illuminating the sample
decreasing the numerical aperture of the objective
increasing the magnification of the objective
staining the sample
6
24.
Under which conditions would the visibility of an object under a microscope be lowest?
;:
C.
d.
e.
25.
If a cellular homogenate was subjected to differential centrifugation, which of the following
would be expected to pellet first?
;:
i.
e.
26.
the endoplasmic reticulum
mitochondria
the cytosol
nuclei
the ribosomes
In preparation for cell fractionation, plasma membrane disruption may be facilitated by placing
the cells in .
;:
::
e.
27.
The object has the same refractive index as the medium
The object and the background each bend light differently
The object difI?acts some but not all of the light rays that hit it
The object absorbs some but not all of the light rays that hit it
The sample is stained with eosin
a hypertonic solution
a hypotonic solution
an acidic solution
an organic solution
none of the above
The lateral difision rates of membrane proteins that contain a fluorescent ligand can be
quantified using a technique called
a.
b.
C.
d.
e.
Single Particle Tracking
Hydrophobicity Plotting
Fluorescence Recovery after Photobleaching
PAGE
Freeze Fracture Electron Microscopy
7
28.
The following are a series of statements. Read them first and then identify the ones that are false
(See the choices a-e below the 5 statements).
1)
2)
3)
4)
5)
Proteins that span a lipid bilayer twice are likely to have their transmembrane segments
arranged as p- sheets.
In SDS polyacrylamide-gel electrophoresis individual protein migrate in the electrical
field at rates determined by their molecular weight: the larger the protein the more it is
retarded by the complex meshwork of polyactylarnide molecules that constitutes the gel
and therefore the more slowly it migrates.
One can determine if a membrane protein is exposed on the external side of the plasma
membrane by digesting with trypsin only if the membrane is intact.
Membranes which have long saturated fatty acid chains will maintain their fluidity at
lower temperatures.
Cholesterol is found in Eukaryotic membranes but not in the membranes of plants and
bacteria.
;:
Statements Statement 5 2 and 3
C.
Statements 1 and 4
Statements 3 and 5
Statements 1 and 3
d.
e.
29.
Movement of phospholipids from one leaflet to the other
t:
“d:
e.
30.
The two leaflets of a biomembrane can be separated and visualized by
::
i:
e.
31.
occurs routinely
requires cholesterol
requires flippases
is impossible
occurs more rapidly than lateral diffusion
.
differential interference contrast microscopy
photobleaching
low angle X-ray scattering
freeze fracture, freeze etch electron microscopy
suspending in non-ionic detergents above the critical micelle concentration
Peripheral membrane proteins
contain a-helical membrane spanning domains
interact with the phospholipid core of the phospholipid bilayer
can be bound to the membrane by interactions with the lipid polar head
contain many amino acids with hydrophobic residues
would not be digested by trypsin in a permeabilized cell
8
32.
Proteins can be anchored to the plasma membrane by all of the following except
::
C.
d.
e.
33.
Which of the following statements is not a feature of pot-ins?
::
ii:
e.
34.
Porins are integral membrane proteins
The amino acid sequences of porins are predominantly polar
Porins are anchored to the membrane by a fatty acyl myristate group
Porins form a pore through which small water-soluble molecules can cross the membrane
Porins contain P-pleated sheets
An amphipathic structure
;:
i:
e.
35.
a hydrocarbon moiety such as famesyl
a fatty acyl group such as palmitate
a glycosylated phospholipid such as glycosylphophatidylinositol
a simple sugar such as mannose
none of the above
is held together by disulfide bonds
contains both hydrophobic and hydrophilic residues
consists of laterally packed b strands
causes a sharp bend in the polypeptide backbone
ontains unsaturated long chain hydrocarbons
All of the following statements correctly describe biomembranes except
t:
C.
d.
e.
each biomembrane in a cell may have a different protein to lipid ratio
the two leaflets of a biomembrane may contain different proteins and phospholipids
some biomembranes have free edges
transmembrane proteins can difFuse freely in most biomembranes
none of the above
CELL BIOLOGY - BIOL 303:
EXAM 2
March 30, 2000
There is only 1 correct answer per question. There are a total of 35 questions. All
questions are of equal weight and there is no partial credit.
Please mark your answers on the Scantron Sheet and woPer/v code in your name
and student ID number. Please use a #2 Pencil. If you have to erase - please erase
cleanly so the Scanner does not make a mistake.
Please write the color of your exam on the top of the Scantron so that we can score
your exam with the correct key.
FINALLY - DON’T PANIC - THINK - READ THE QUESTION AT LEAST TWICE
BEFORE YOU ANSWER !
MAKE SURE YOU MARK THE SCANTRON BOX YOU MEAN TO MARK !!!!
1.
The major difference between fatty acid metabolism in mitochondria vs. fatty acid
metabolism in peroxisomes is:
a.
b.
C.
d.
e.
2.
When ATP is hydrolyzed to ADP + Pi
a.
b.
C.
d.
e.
3.
Two high energy phosphoanhydride bonds are cleaved
2 kcal are released for each of the two AMP bonds per ATP molecule
7.3 kcal is released for the two phosphanhydride bonds per ATP molecule
Energy is consumed
None of the above
According to the chemiosmotic paradigm
a.
b.
C.
d.
e.
4.
Fatty acid metabolism in peroxisomes results in the generation of more
ATP than fatty acid metabolism in mitochondria.
Fatty acid metabolism and ATP generation in mitochondria do not involve
electron transport, while fatty acid metabolism and ATP generation in
peroxisomes do involve electron transportIn mitochondria fatty acid metabolism results in ATP biosynthesis, while in
peroxisomes fatty acid metabolism does not result in ATP biosynthesis.
Fatty acid metabolism in mitochondria yields more triacylglycerol than
fatty acid metabolism in peroxisomes.
Twu of the above.
The proton motive force (PMF) is the result of the electric membrane
potential established by the pumping of protons against the prevailing
proton gradient and the stepwise transfer of electrons between carrier
complexes.
The pumping of protons from the intramembranous space to the matrix of
mitochondria establishes a PMF that drives ATP synthesis.
ATP synthesis is dependent on an electron gradient that is formed by
pumping electrons from the mitochondrial matrix to the intramembranous
space.
The movement of protons across the proton concentration gradient does
not require energy because the movement is in the direction of higher
concentration to lower concentration of protons.
Two of the above
During electron flow from NADH to 02, each of the major enzyme complexes
located in the inner membrane
a.
b.
C.
d.
e.
Uses all of each electron’s potential energy to transport protons into the
mitochondrial matrix.
Uses all of each electron’s potential energy to transport protons out of the
matrix.
Uses a portion of each electron’s potential energy to transport protons
into the matrix.
Uses a portion of each electron’s potential energy to transport protons out
of the matrix.
None of the above
5.
In anaerobic metabolism
a.
b.
::
e.
6.
During glycolysis
a.
b.
::
e.
7.
Glucose is converted to alcohol, and there is a net production of 2 ATP
molecules and 2 NADH molecules per molecule of glucose.
There is an initial investment of 2 ATP molecules, and a net production of
2 ATP molecules per molecule of glucose.
CO* is produced.
Enzymes in the mitochondrial matrix and inner mitochondrial membrane
metabolize glucose.
Two of the above.
Following glycolysis
a.
b.
::
e.
8.
Yeast convert fatty acids + NADH to ethanol, CO, + NAD’ in the process
of fermentation.
Muscle cells convert pyruvate to lactic acid + NAD’.
Oxygen is an essential reactant.
Glucose is hydrolyzed to yield CO, + NADH.
None of the above.
Pyruvate combines with coenzyme A (CoA) to yield acetyl CoA.
Acetyl CoA enters the TCA cycle by reacting with a 6 carbon molecule.
Acetyl CoA enters the TCA cycle by reacting with a 5 carbon molecule.
Acetyl CoA is hydrolyzed to CO, + H,O.
None of the above.
For every acetyl CoA molecule entering the TCA cycle
a.
b.
ii:.
e.
2 COZ molecules, 3 NAD’ molecules, 1 FAD molecule, and 1 GTP
molecule are produced.
3 molecules of NAD’ and 1 molecule of FAD are hydrolyzed.
3 molecules of NADH and 1 molecule of FADH* are oxidized.
3 molecules of NAD’ and 1 molecule of FAD are reduced.
Two of the above.
9.
An experiment was discussed in class in which proton transport across
mitochondria was shown to be coupled to electron transport from NADH and
FADH, to 0,. In this experiment
a.
b.
::
e.
10.
In another experiment discussed in class, inner mitochondrial membranes were
sonicated to produce inside-out vesicles. These vesicles were further treated by
mechanical agitation.
a.
b.
C.
d.
e.
11.
Movement of protons was measured by pH changes in the solution
surrounding the mitochondria.
The coupling only occurred in the absence of 0,.
An electron donor (NADH) had to be present.
ATP was produced.
Two of the above.
The vesicles were capable of ATP synthesis, but incapable of electron
transport.
This experiment demonstrated that the protein that pumps protons is a
peripheral membrane protein.
This experiment demonstrated that the protein that synthesizes ATP is an
integral membrane protein.
The vesicles were capable of electron transport, but were not capable of
ATP synthesis, while the released F, particles were incapable of electron
transport or ATP synthesis.
None of the above.
Which of the following statement(s) about mitochondria and chloroplasts is (are)
not true?
a.
b.
C.
d.
e.
Mitochondria and chloroplasts are both surrounded by 2 lipid bilayer
membranes.
Most proteins involved in photosynthesis are encoded by genes in
chloroplast DNA, while most proteins of mitochondria are encoded by
nuclear genes.
The current hypothesis on the origin of mitochondria and chloroplasts is
that they evolved from photosynthetic and non-photosynthetic bacteria
that were incorported into ancestral eukaryotic cells.
With evolutionary time, many bacterial genes from mitochondria and
chloroplasts have been transferred to the nucleus of eukaryotic cells.
Two of the above.
12.
Proteins encoded in nuclear DNA and targeted to mitochondria
a.
b.
C.
d.
e.
13.
which of the following experiments/observations provide(s) evidence that
proteins transported into mitochondria must be unfolded when they traverse the
membrane channel?
a.
b.
::
e.
14.
Are usually synthesized on cytosolic ribosomes not bound to the ER.
Have a COOH terminal targeting sequence consisting of -20 consecutive
negatively charged amino acids that is almost identical among all proteins
targeted to mitochondria.
Always have one targeting sequence at their NH, end that directs them to
the mitochondria and a 2”d targeting sequence at their COOH end that
directs them to the appropriate subcompartment within the mitochondria.
Always have one targeting sequence that enables them to pass through
the outer mitochondrial membrane into the inter-membrane space, and a
2”d targeting sequence that enables them to pass through the inner
mitochondrial membrane into the matrix.
Two of the above.
Conversion of cytosolic proteins to mitochondrial proteins when a matrix
targeting sequence (MTS) is fused to the cytosolic protein structural gene.
Blocking ATP hydrolysis in the cytoplasm does not interfere with transport
of proteins into mitochondria.
Deletion of the MTS from mitochondrial proteins.
Addition of the DHFR inhibitor to a fusion protein consisting of a MTS
fused to the DHFR structural gene.
None of the above.
Proteins that are transported to subcompartments of mitochondria
a.
b.
C.
d.
e.
May contain a MTS that targets them to the matrix
May contain a MTS that targets them to the matrix plus a stop transfer
sequence that anchors them in the inner mitochondrial membrane.
Are first anchored in the outer mitochondrial membrane and then
transferred to the inter-membrane space or the inner membrane.
Retain their targeting sequences when they get to their final destination.
Two of the above.
15.
Which of the following statements about protein transport to peroxisomes is not
1
true?
a.
b.
C.
d.
e.
16.
A protein with the following topogenic features: signal peptide, stop-transfer
sequence, signal-anchor sequence, and stop-transfer sequence arranged
sequentially, N --) C, and separated by various sequences of hydrophilic amino
acids has
a.
b.
C.
d.
e.
17.
Peroxisomes have only one membrane so incoming proteins from the
cytoplasm only have to traverse one membrane to get to the peroxisome
lumen.
Proteins destined for peroxisomes are properly folded before transport.
Proteins destined for peroxisomes have a targeting sequence at their NH,
end that binds to a receptor in the lumen of the peroxisome.
Peroxisomes do not have a PMF, so electron transport is not required for
protein transport.
Two of the above.
3 transmembrane segments with the N- and C-terminus
protein on opposite sides of the ER membrane.
3 transmembrane segments with the N- and C-terminus
protein on the same side of the ER membrane.
4 transmembrane segments with the N- and C-terminus
protein on opposite sides of the ER membrane.
4 transmembrane segments with the N- and C-terminus
protein on the same side of the ER membrane.
None of the above.
of the mature
of the mature
of the mature
of the mature
You have synthesized an ER-targeted protein in an in vitro protein synthesizing
system and in the absence of microsomes. You add microsomes posttranslationally to this system.
E:
C.
d.
e.
The protein is translocated across the ER membrane.
The protein is folded prematurely and hence does not translocate into the
ER.
The signal sequence of the protein is cleaved off before the protein is
transported into the ER.
After translation is completed, SRP binds the ribosome and signal
sequence to the microsomal membranes.
Two of the above.
18.
Yeast set mutants have been useful in dissecting the secretory pathway for all
the following reasons except
a.
b.
C.
d.
e.
19.
Evidence that transport of proteins progressively from the cis + medial ---) trans
Golgi compartments occurs by cisternal progression and maturation includes
a.
b.
C.
d.
e.
20.
The association of many small vesicles with the Golgi complex.
The experiment showing that cleavage of the signal sequence from the
translated protein inhibits passage from the cis --) medial * trans Golgi
compartments.
The observation that aggregated collagen is never seen in small vesicles
near the Golgi cistemae.
The observation that newly synthesized radiolabeled secreted proteins
are frequently seen in small vesicles near the Golgi cistemae.
None of the above.
In the absence of any signal or targeting sequence, the expected subcellular
location for any protein is
a.
b.
S:
e.
21.
Isolation of mutants allowed the identification of key phenotypic classes.
Analysis of double mutants permitted the sequential order of events to be
determined.
Isolation of mutants raised the possibility of subsequent identification of
specific gene products.
Isolation of temperature mutations lead to the ability to grow yeast
productively at lower temperatures than previously possible.
Two of the above.
Mitochondria
Lysosome
Nucleus
Plasma membrane
Cytosol
Protein disulfide isomerase normally has a C-terminal KDEL sequence. In the
absence of such a sequence, the protein is
a.
b.
::
e.
Subject to quality control mechanisms within the ER and hence exported
to the cytosol for degradation by the proteosome.
Secreted from the cell.
Transported to lysosomes where it is degraded.
Aggregated within the ER into crystalline arrays.
None of the above.
22.
Failure to add mannose 6-phosphate residues to glycoproteins results in
I
t:
::
e.
23.
The hemagglutinin (HA) protein of influenza virus is a trimer of three monomeric
subunits. Before leaving the ER, the protein must do all of the following except
a.
b.
C.
d.
e.
24.
b.
C.
d.
e.
Are exported via a translocon to the cytoplasm where they are
ubiquinated and degraded by the proteosome.
Are transported to the Golgi where they have another chance to fold
property.
Are transported to lysosomes where they are degraded.
Are exported from the ER by retrograde vesicular transport and degraded
in the cytoplasm.
None of the above.
Which of the following statements is not true about glycosylation of proteins?
a.
b.
Z.
e.
26.
become glycosylated
fold
form the proper disulfide bonds
Assume the proper quaternary configuration
fuse the viral envelope with the ER membrane
Some proteins that are not properly folded in the ER
a.
25.
Retention of proteins in the ER
Retention of proteins in the Golgi
Retention of proteins in lysosomes
Failure of proteins to be transported to lysosomes
a plasma membrane malfunction
N-linked oligosaccharides are complex, multi-branched structures that are
added to proteins in the ER.
N-linked oligosaccharides are added in the ER and modified in the Golgi.
O-linked oligosaccharides are simple, not highly branched structures.
Oligosaccharide components are usually not required for protein function,
stability, or proper folding.
Two of the above.
Once internalized, LDL and transferrin are
a.
b.
C.
d.
e.
Both recycled to the cell surface
Both degraded in lysosomes
sorted in different ways such that LDL is degraded and transferrin is
recycled
sorted in dierent ways such that LDL is recycled and transferrin is
degraded
None of the above
27.
Which of the following statements is not true about proteins that are sorted
based on their expression in the basolateral or apiwl surface of a cell?
a.
b.
C.
d.
e.
28.
Which of the following statements is not true about clathrin-coated vesicles?
::
C.
d.
e.
29.
Clathrin-coated vesicles have a cage-like structure formed by triskelions.
The assembly particles of clathrin-coated vesicles promote polymerization
into cages.
The dynamin of clathrin-coated vesicles selectively binds to different
proteins in the membrane and determines which proteins will be
transported.
Budding off of clathrin-coated vesicles is a GTPdependent event.
None of the above.
COP I vesicles
Z:
::
e.
30.
Insertion into the apical face is directed by a sorting signal imbedded in
the protein sequence.
Proteins sorted to the basolateral face are held in place by ankyrin, while
proteins sorted to the apical face are held in place by stickin.
Some apical proteins are first inserted into the basolateral face,
endocytosed into vesicles, and then transferred via transcytosis to the
apical face.
Some basolaterat proteins are first inserted into the basolateral face,
endocytosed into vesicles and then re-inserted into the basolateral face.
Two of the above.
Mediate retrograde transport from the Golgi to the ER.
Mediate retrograde transport from the cis Golgi to the trans Golgi.
Contain a receptor that recognizes mannose+phosphate.
Bud by a GTP-independent process.
TM of the above.
Which of the following statements is not true for COP II vesicles?
2
C.
d.
e.
Mediate transport from the ER to the Golgi.
Are similar to COP I vesicles except have different coat proteins.
Contain the protein dynamin which is responsible for selecting proteins for
transport.
Fuse to form ER-Golgi intermediate compartments if the Golgi is distant
from the ER.
Two of the above.
31.
ATP-powered pumps:
a.
b.
C.
d.
e.
32.
Facilitated transport can be distinguished from passive diffusion by all of the
following relationships except:
a.
b.
::
e.
33.
the rate of transport is much higher than that predicted from the partition
coefficient.
the rate of transport is stereochemcially specific.
the rate of trasnsport saturates as substrate concentration increases.
the rate of transport is described by the Nemst equation.
the rate of transport is independent of the partition coefficient.
The membrane potential in animal cells largely depends on:
::
i.
e.
34.
transport ions or small molecules down a concentration/electric-potential
gradient
produce an equilibrium distribution of the transported ion across the
membrane
transport ions or small molecules up a concentration/electric-potential
gradient
can readily derive energy from other nucleoside triphosphates such as
GTP
facilitate diffusion of low molecular weight molecules through the
membrane
Ca2+ channels
K+ channels
Mg2+ channels
Na’ channels
Ca’ dependent ATPases
The energy requirement for the transport of K+ out of a cell is the sum of
a.
b.
::
e.
Fick’s law plus the Nemst equation
the total electrostatic energy potential of a tissue plus the concentrative
energy potential across the tissue
both thermodynamic and kinetic energy contributions
the free-energy change generated by the K+ concentration gradient plus
the free-energy change generated from the membrane electric potential
two of the above
35.
F- and V-class pumps are very similar to each other in:
2
::
e.
their subcellular distribution
their subunit composition
the wide range of cations transported by both
the specific subunit that is phosphorylated as transport occurs
all of the above
CELL BIOLOGY - BIOL 303
!
EXAM 3
April 25, 2000
There is only 1 correct answer per question. There are a total of 30 questions. All
questions are of equal weight and there is no partial credit.
Please mark your answers on the Scantron Sheet and properly code in your name and
student ID number.
Please use a #2 Pencil. If you have to erase - please erase cleanly so the
Scanner does not make a mistake.
Please write the color of your exam on the top of the Scantron so that we can swre
your exam with the correct key.
FINALLY - DON’T PANIC - THINK - READ THE QUESTION AT LEAST TWICE
BEFORE YOU ANSWER !
MAKE SURE YOU MARKED THE SCANTRON BOX YOU MEANT TO MARK !!!!
1. Actin-binding proteins that generate actin filament bundles
a. are long and flexible
b. bind only at the ends of actin filaments
c. have only one actin binding site
d. are short and inflexible
e. two of the above
2. Decoration of actin filaments with myosin Sl is commonly used to
a. attach actin filaments to cell membranes
b. disassemble actin filaments
c. reveal the polarity of actin filaments
d. reveal the polarity of myosin filaments
e. measure the force of muscle contraction
3. All of the following statements about actin assembly are correct except
a. ADP-actin can assemble into filaments
b. actin subunits can treadmill through an actin filament
c. actin assembly can produce force for movement
d. actin (-) ends assemble more rapidly than actin (+) ends
e. actin assembly has a slow phase and a rapid phase
4. Which portion of myosin interacts with actin filaments?
a. the head domain
b. the rod domain
c. the light chains
d. the tail domain
e. the GTP binding domain
5. Which of the following properties is not shared by all myosins?
a. the ability to bind ATP
b. the ability to form dimers
c. the ability to bind actin
d. the presence of a head domain
e. the presence of a tail domain
6. What is the function of CapZ and tropomodulin in the sacromere?
a. to center myosin thick filaments
b. to attach actin thin filaments to the Z disk
c. to maintain a constant actin thin filament length
d. to make contraction sensitive to Ca2+
e. to expose myosin binding sites on the actin microfilament
acts to keep.myosin-thick filaments in the center of the sarcomere.
7.
a. Nebulin
b. Titin
c. alpha-actinin
d. CapZ
e. Tropomyosin
8. If you compared under the microscope a contracted sarcomere to a relaxed
sarcomere which of the following regions would not differ in width ?
a. the A band
b. the I band
c. the H zone
d. the entire sarcomere
e. the material between the Z lines
9. Which of the following is responsible for the Ca2+-dependent activation of myosin
which is independent of excitation coupling ?
a. troponin C
b. tropomyosin
c. myosin light chain kinase
d. tropomodulin
e. Ca2+ ATPase
10. The sarcoplasmic reticulum must have integral membrane proteins that can
a.
b.
c.
d.
e.
release and pump Ca2+
bind to tropomyosin and troponin
undergo action potential
stimulate the outgrowth of t-tubules
stimulate ATP hydrolysis
11. Vesicle transport along actin filaments is driven by
a. actin polymerization
b. myosin I
c. contraction
d. myosin II
e. actin treadmilling
12. Multinucleated cells may result from a defect in
.
a. myosin V
b. myosin I
c. stress fiber formation
d. myosin II
e. profilin
13. Membrane extension during cell locomotion is driven by
a. myosin II
b. actin depolymerization
c. contraction
d. actin polymerization
e. integrin receptor interactions with the extracellular matrix
14. Which of the following is essential for treadmilling to occur down the length of an
actin filament ?
a. the presence of tropomyosin and troponin
b. asymmetry in the rates of polymerization and depolymerization occurring at the two
ends of the filament.
c. stability of the actin filament
d. none of the above
e. two of the above
15. A microtubule protofilament is formed by the
a.
b.
c.
d.
e.
lateral association of only alpha-tubulin subunits
head-to-tail association of only beta-tubulin subunits
lateral association of tubulin dimers
head-to-tail association of tubulin dimers
interspersion of alpha, beta and gamma tubulin monomers
16. At MTOCs, microtubule nucleation is facilitated by
a.
b.
c.
d.
e.
centrioles
gamma-tubulin
GDP-tubulin dimers
basal bodies
centromere
17. Growing microtubule ends are normally “stabilized” by
a. a GDP cap
b. a GTP cap
c. phosphorylation of tubulin subunits
d. gamma-tubulin
e. dephosphorylation of tubulin subunits
18. The drug taxol acts to
a.
b.
c.
d.
e.
.
block microtubule disassembly
promote microtubule assembly
promote cell division
sever microtubules
blocks cytokinesis
19. The region of the kinesin motor protein that interacts with the motors cellular cargo
is the
a. head domain
b. tail domain
c. rod domain
d. the wiled coil domain
e. the regulatory chains
20. All of the following statements describe kinesin except
a. Kinesin is a (-) end-directed motor
b. Kinesin transports vesicles along microtubules
c. Kinesin binds and hydrolyzes ATP to produce movement
d. Kinesin is composed of two heavy chains and two light chains
e. Kinesin carries out anterograde transport
21. The force for axoneme bending is derived from the
a.
b.
c.
d.
e.
sliding movement of central pair microtubules
contraction of central pair microtubules
sliding movement of outer-doublet microtubules
contraction of outer doublet microtubules
the action of kinesin motors
22. The
microtubules.
a.
b.
c.
d.
e.
serves as a template for the unusual structure of axoneme
gamma-tubulin ring complex
pericentriolar material
centrosome
basal body
kinetochore
23. Separation of spindle poles during spindle formation and anaphase B most likely
depends on which of the following?
a. (+) end directed microtubule motors at the cell cortex
b. (+) end directed microtubule motors at the kinetochore
c. (-) end directed microtubule motors in the microtubule overlap zone
d. (+) end directed microtubule motors in the microtubule overlap zone
e. depolymerization of the kinetochore microtubules
24. Which of the following occurs during anaphase A?
a. the spindle elongates
b. shortening kinetochore microtubules move chromosomes toward the spindle poles
c. chromosomes move to the spindle equator
d. the spindle poles move closer together
e. the astral microtubules shorten
25. Which type of spindle microtubules are attached to chromosomes ?
a. astral microtubules
b. kinetochore microtubules
c. polar microtubules
d. all of the above
e. none of the above
26. If at metaphase there is a mono-attached chromosome
a. the cell cycle will progress to anaphase A
b. the cell cycle will progress to anaphase B
c. there will be chromosome nondisjunction
d. the cell cycle will restart
e. the cell cycle will arrest at metaphase
27. Which of the following would NOT be consistent with our current understanding
of cytokinesis ?
a. anti-myosin II antibodies injected in a dividing cell cause cytokinesis to stop.
b. when the myosin II gene is mutated cells undergo nuclear division but not
cytokinesis.
c. anti-actin antibodies injected into dividing cells have no effect on cytokinesis
d. actin filaments seen in micrographs are aligned parallel to the cleavage furrow
e. when the myosin I gene is mutated cytokinesis proceeds normally
28. All of the following statements describe intermediate filaments except
a. the subunits are rod-like
b. most types of intermediate filament subunits cannot co-polymerize
c. intermediate filaments are resistant to harsh conditions that normally denature
proteins
d. intermediate filaments assemble and disassemble in the cell
e. new subunits are added to the ends of the filaments
29. In the cell, intermediate filament disassembly is triggered by
a. hydrolysis of ATP bound to the subunits
b. phosphorylation of the subunits
c. the binding of Ca2+ to the subunits
d. the hydrolysis of GTP bound to the subunits
e. none of the above
30. In which of the following ways are intermediate filaments similar to both
microtubules and microfilaments ?
a. IFS are a chemically heterogeneous group of structures
b. IFS assemble and disassemble under changing cellular conditions
c. IFS have been identified in animal cells but not in other eukaryotes
d. IFS assemble into structures of varying thickness via several different pathways
e. all of the above
CELL BIOLOGY - BIOL 303
’
EXAM 4
May 18,200O
There is only 1 correct answer per question. There are a total of 30 questions. All
questions are of equal weight and there is no partial credit.
Please mark your answers on the Scantron Sheet and properly code in your name and
student ID number.
Please use a #2 Pencil. If you have to erase - please erase cleanly so the
Scanner does not make a mistake.
Please write the color of your exam on the top of the Scantron so that we can score
your exam with the correct key.
WRITE EXAM 4 ON YOUR SCANTRON AND WHEN YOU HAND IT IN PUT IT IN THE
BOX THAT SAYS EXAM 4.
FINALLY - DON’T PANJC - THINK - READ THE QUESTION AT LEAST TWICE
BEFORE YOU ANSWER !
MAKE SURE YOU MARKED THE SCANTRON BOX YOU MEANT TO MARK !!!!
YOU HAVE 2 HOURS TO COMPLETE BOTH EXAMS
1. Cells that have exited the cell cycle
A) can stay indefinitely in Gz
B) can stay indefinitely in GO
C) can re-enter the cell cycle at S
D) die
E) two of the above
2. Which of the following events does not occur during M phase?
A) Chromosomes are completely condensed and visible as individual
structures.
B) Microtubule spindle fibers extend from centrosomes to chromosomes and
from the centrosome at one pole of the cell to the centrosome as the
opposite pole of the cell.
C) Sister chromatids separate during anaphase.
D) Nuclear membrane disappears during telophase.
E) two of the above.
3. Which of the following statements is not true.
A) The cell cycle is controlled by cyclins and cyclin dependent kinases (cdk);
Cyclins are the regulatory subunit, while cdk’s are the catalytic subunit.
8) The level of cyclins remains constant throughout the cell cycle, while the
level of cdk’s changes.
C) Each cdk can associate with multiple cyclins.
D) A cyclin is activated when a cdk binds to it.
E) None of the above.
4. ~53 is a regulatory protein that is also called a “tumor suppressor.” Which of the
following statements is not true about ~53 and the cellular processes in which it
is involved?
A) Cells with high levels of wild type ~53 protein cycle faster than cells with
low levels of ~53.
B) ~53 exerts its effects on DNA repair by stimulating transcription of P*‘~“.
C) If DNA damage is very high, then ~53 causes cellular apoptosis.
D) Many tumor cells have mutations in the ~53 gene.
E) Two of the above.
5. Which of the following experiments/statements supports the hypothesis that the
cell cycle is regulated by soluble factors such as cyclins’and cyclindependent
kinases?
B)
Cl
D)
El
The cell cycle can proceed either forwards or in reverse, demonstrating
that soluble factors sequestered in the cytoplasm can be released at any
time and cause cycling.
When a cell in Gl phase is fused to a cell in S phase and the resulting
heterokaryon is pulsed with 3H-thymidine, the 3H-thymidine is only
incorporated into the DNA of the S phase cell.
When a cell in Gl phase is fused to a cell in S phase and the resulting
heterokaryon is pulsed with 3H-thymidine, the 3H-thymidine is
incorporated into the DNA of both nuclei.
GO mammalian cells stimulated with a growth factor and simultaneously
microinjected with antibodies to the soluble molecule cyclin D will
replicate their DNA.
None of the above.
6. In paracrine signaling, the signaling molecule
A)
B)
C)
D)
E)
acts on target cells far away from the secreting cell
acts on target cells in close proximity to the secreting cell
acts on the same cell that secretes the signaling molecule
is carried to the target cell by the blood
is bound to the cell surface
7. All of the following statements about the following hormones and their receptor are
true except
A)
6)
C)
D)
E)
8.
insulin binds to a cell surface receptor
prostaglandins bind to cell surface receptors
estrogen binds to an intracellular receptor
thyroxine binds to a cell surface receptor
two of the above
Binding of epinephrine to b-adrenergic receptors
A)
B)
C)
D)
E)
leads to an increase in cAMP
causes muscle cells of the intestine to constrict
causes arteries to relax
leads to a repression of adenylyl cyclase
leads to an activation of guanylyl cyclase
9.
Which of the following statements about Gs-protein-coupled receptors is not true?
A)
B)
C)
0)
Gsa is bound to GDP in the absence of ligand bound to the receptor.
Gsa bound to GDP activates adenylyl cyclase.
Binding of receptor to Gsa induces a conformational change in Gsa.
Binding of the hormone to the receptor causes a conformational change in
the receptor.
E) two of the above
10. Receptor tyrosine kinase proteins contain all of the following structural features
except
A) an extracellular ligand binding domain
B) a cytosolic phosphatase domain
C) a cytosolic kinase domain
D) a dimerization domain
E) a transmembrane domain
11. Binding of hormone to a receptor tyrosine kinase causes all of the following
except
A)
B)
C)
D)
E)
12.
All of the following are true about GAP proteins except
A)
B)
C)
D)
E)
13.
dimerization of the receptor
autophosphorylation of the receptor
activation of Ras through an interaction with GRB2 and SOS proteins
hydrolysis of GTP bound to Ras
none of the above
they increase the rate of GTP hydrolysis
they decrease the duration of the effector response
they increase the rate of G protein recycling
they interact with GTP bound G proteins
they interact with GDP bound G proteins
Cholera toxin acts by
A) preventing GTP binding to G proteins
B) preventing GEFs binding to G proteins
C) preventing G proteins from hydrolyzing GTP
D) preventing G proteins from interacting with effector molecules
E) none of the above
14. All of the following steps are part of the kinase cascade that transmits signals
!
down from activated Ras protein except
A)
B)
C)
D)
E)
15.
ras phosphorylates Raf
raf phosphorylates MEK
MEK phosphorylates MAP kinase
MAP kinase phosphorylates target proteins
A GEF activates ras
Which of the following is not a common intracellular second messenger?
A) 1,2diacylglycerol (DAG)
B) inositol 1,4,5-trisphosphate (IP3)
C) adenosine triphosphate (ATP)
D) 3’,5’-cyclic GMP (cGMP)
E) Ca++
16.
All of the following statements about nitric oxide signaling are true except
A)
B)
C)
D)
E)
Nitric oxide is synthesized by nitric oxide synthase from arginine and oxygen.
Nitric oxide is a gas.
Nitric oxide activates the soluble form of guanylate cyclase.
Nitric oxide has a half-life of greater than five minutes in tissues.
Nitric oxide acts by a paracrine mechanism
17. Which of the following reactions does not play a role in the G protein-cAMP
pathway?
A)
B)
C)
D)
E)
18.
Gs protein activation of adenylyl cyclase
Ras activation of MAP kinase
cAMP activation of PKA
CREB binding to CRE
two of the above
The intracellular organelle involved in the triggering cascade for apoptosis is?
A)
B)
Cl
D)
El
chloroplast
mitochondrion
nucleus
Zellweger’s body
endoplasmic reticulum
The activation of Ras by the binding of integrin receptors, tyrosine kinase
receptors and G protein coupled receptors to their ligands is an example of
A) divergent signaling
B) receptor cross talk
C) convergent signaling
D) receptor interference
E) none of the above
The execution phase of programmed cell death is characterized by all of the
following except
A) nuclear shrinkage
B) loss of adhesion to neighboring cells
C) chromatin fragmentation
D) formation of blebs at the cell surface
E) cell lysis
During the process of extravasation in which leukocytes leave the blood stream
and migrate through the epithelial wall of the blood vessels
A) Infection or inflammation in the area near the blood vessel wall causes
the epithelial cells to become activated which results in exocytosis of
cytoplasmic vesicles containing P-selectin.
B) P-selection is expressed on the side of the epithelial cell facing the area
of inflammation or infection.
C) The binding of P-selection on the epithelial cell plasma membrane to
Lewis x on the leukocyte is very high affinity and is sufficient to cause the
leukocyte to stick tightly to the epithelial layer.
D) lntegrins on the leukocyte plasma membrane inhibit binding of the
leukocyte to epithelial cells.
E) Two of the above.
22. Which of the following experiments supports the hypothesis that cadherins
mediate adhesion?
A) Dissociated cultured epithelial cells aggregate when antibodies to
cadherin are added to the cultures.
B) Fibroblasts do not express cadherins and do not aggregate in culture.
However, when fibroblasts are transfected with a gene encoding Ecadherin, the resulting transfected cells form aggregates.
C) Removal of Ca+* from the growth medium of aggregated epithelial cells
does not affect epithelial cell adhesion.
D) If 1000 fibroblast cells transfeded with P-cadherin are mixed together with
1000 fibroblast cells transfected with E-cadherin, no aggregates are
formed.
E) Two of the above.
23. Gap junctions between cells were first identified by electron microsocopy and
A) block transport of all molecules between cells.
B) allow the transport of large molecules such as insulin from one cell to
another cell.
C) contain adaptor proteins that connect cadherin to actin and myosin
filaments in the cytoplasm.
D) can be functionally tested by injecting fluorescently labeled small
molecules into one cell and observing the fluorescent tag pass into an
adjacent cell.
E) None of the above.
24. Which of the following statements about the extracellular matrix (ECM) is not
m?
A)
B)
C)
D)
E)
The ECM helps cells maintain their shape.
The ECM provides a pathway along which cells can migrate.
lntegrins are the most abundant proteins in the ECM.
lntegrins attach cells to their ECM.
Two of the above.
25. Collagen
L
A) is a major component of the basal lamina which is a thin extracellular
structure that underlies many types of cells and connects cells to their
ECM.
B) is a minor component of the ECM, but it is the component that gives the
ECM its elasticity.
C) fibers are very elastic because the individual fibriles that make up each
fiber slide along each other allowing the fiber to elongate and contract.
D) fibers by themselves cannot withstand much force and require additional
proteins such as fibronectin and laminin for strength.
E) Two of the above.
26. Benign tumors and malignant tumors
A) differ from each other in that many cells of malignant tumors are in
mitosis, while most cells of benign tumors are in G,,.
B) both invade surrounding normal tissue.
C) break through their underlying basal lamina to enter adjacent blood
vessels.
0) differ from each other in that benign tumors are frequently encapsulated,
while malignant tumors are not.
E) Two of the above.
27. Cancer cells are able to spread to distant parts of the body and form tumors
there (metastasize) because
A)
B)
C)
D)
E)
they secrete enzymes that digest their underlying basal lamina.
they can enter adjacent blood vessels and travel to distant sites.
they secrete factors that destroy neighboring blood vessels.
they are unable to adhere to surrounding tissues.
Two of the above.