1. which of the following statements are correct in...
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1. Which of the following statements ARE CORRECT in describing cell membranes?
Cell membranes …
(1) are primarily made up of membrane lipids and proteins.
(2) define boundaries between the cytosol, organelles, and extracellular environment.
(3) transport hydrophobic molecules between compartments in the cell.
(4) allow the passive diffusion of ions across the lipid bilayer.
(5) regulate the movement of charged molecules between compartments in the cell.
a) 1, 3, 4
b) 2, 3, 5
c) 1, 2, 5
d) 1, 2, 3, 4
e) 1, 2, 3, 5
2. What are some of the basic properties of ALL transmembrane proteins?
ALL transmembrane proteins ...
a) are amphipathic α-helical proteins that span the lipid bilayer.
b) are anchored to the cell membrane by a lipid anchor.
c) have hydrophobic domains that interact with the aqueous cellular environment.
d) have transmembrane domains composed of α-helices or β-sheets spanning the lipid bilayer.
e) are glycosylated on the cytosolic side of the cell membrane.
3. What is the importance of the K+ Leak channel in generating the membrane potential across animal plasma membranes?
a) Excess (+) charges accumulate on the outside of the plasma membrane due to the K+ Leak channels transporting K+ out of the cell by active transport.
b) K+ is transported down its electrochemical gradient into the cell by K+ Leak channels, leading to excess (+) charges inside.
c) When there is a high cytosolic [K+], the K+ Leak channels open and release excess K+ out of the cell, leading to excess (+) charges on the outside.
d) K+ Leak channels use the Na+ electrochemical gradient to transport K+ to the inside of the cell, leading to excess (+) charges inside.
e) K+ is passively transported out of the cell through the K+ Leak channels, leading to excess (+) charges on the outside.
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4. A scientist measured the movement of Cl- and NO3- into a plant vacuole and found that
these ions were being transported against their concentration gradients. What is the transport mechanism responsible for this?
Cl- and NO3- are transported by …
a) PPi -powered pumps using PPi hydrolysis as the source of energy.
b) symporters using the proton motive force.
c) Cl-/NO3- pumps using energy from ATP hydrolysis.
d) Cl- and NO3- channels, driven by the proton motive force.
e) antiporters using energy from a H+ gradient.
5. Which of the following statements ARE CORRECT in describing how the Na+/glucose symporter transports solutes?
(1) Na+ and glucose are transported against their electrochemical gradients.
(2) Binding of Na+ increases the affinity of the symporter for glucose.
(3) ATP hydrolysis provides the energy for transport.
(4) Na+ and glucose are transported into the cytosol.
(5) The Na+ electrochemical gradient provides energy for the transport of glucose.
a) 1, 3
b) 2, 4
c) 1, 2, 3
d) 2, 3, 4
e) 2, 4, 5
6. How do Channel Proteins function in transporting ions across a cell membrane?
Channel Proteins function by …
a) using the energy from ATP hydrolysis to transport ions.
b) passive transport of ions down their electrochemical gradients.
c) moving one molecule at a time with each cycle of opening and closing.
d) active transport of ions down their electrochemical gradients.
e) passive diffusion of ions down their concentration gradients.
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7. What is the role of ATP hydrolysis for the Na+/K+ pump? ATP hydrolysis ….
a) leads to phosphorylation and regulation of the Na+/K+ pump conformation.
b) provides energy to transport Na+ and K+ down their electrochemical gradients.
c) is required to release Na+ and K+ bound to the Na+/K+ pump.
d) provides energy for Na+ and K+ to simultaneously bind to the Na+/K+ pump.
e) leads to the phosphorylation and inactivation of the Na+/K+ pump.
8. A scientist discovered two new glucose uniporters, called GLUT7 and GLUT8. The scientist expressed each glucose uniporter in an animal cell line (which lacks glucose transporters) and measured the rate of glucose uptake by the cell line under different glucose concentrations. The scientist determined the following data: GLUT7 has a Km of 3 mM glucose; GLUT8 has a Km of 15 mM glucose. Which of the following statements IS THE CORRECT conclusion?
a) GLUT8 has a higher affinity for glucose when compared with GLUT7.
b) GLUT7 transports 1 glucose molecule each cycle while GLUT8 transports 5 glucose molecules each cycle.
c) GLUT7 has a higher affinity for glucose when compared with GLUT8.
d) Glucose is transported at a faster rate by GLUT8 in comparison with GLUT7.
e) At a concentration of 15 mM glucose, only GLUT8 transport will be saturated.
9. Which of the following statements ARE CORRECT in describing how ATP Synthases function?
(1) ATP synthases use energy from the flow of H+ down the H+ electrochemical gradient.
(2) ATP synthases function at the plasma membrane in plant and animal cells.
(3) The rotation of the rotor leads to conformation changes in the β subunits catalyzing ATP synthesis.
(4) The H+ electrochemical gradient is generated from electron transport processes.
(5) The synthesis of ATP provides the energy to pump H+ through the β subunits against their electrochemical gradient.
a) 1, 3, 4
b) 2, 3, 5
c) 1, 2, 4
d) 3, 4, 5
e) 2, 3, 4, 5
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10. For protein sorting to mitochondria, which of the following steps IS FALSE?
A protein destined for the mitochondrial matrix ….
a) has an N-terminal amphipathic α-helix signal sequence.
b) is synthesized and fully folded in the cytosol.
c) is recognized, through its mitochondrial signal sequence, by a receptor in the TOM complex.
d) is translocated across the outer membrane through the TOM complex.
e) is translocated across the inner membrane through the TIM23 complex.
11. What role does GTP play in the sorting of proteins to the Endoplasmic Reticulum (ER)?
GTP is required for …
a) the Signal Recognition Particle (SRP) to recognize the ER signal sequence as this signal sequence emerges from the ribosome.
b) delivering the ribosome and developing protein to the translocator channel in the ER membrane.
c) binding of the SRP-ribosome complex to the SRP receptor at the ER membrane.
d) dissociation of the SRP bound to the SRP receptor.
e) translocation of the developing protein to the ER lumen.
12. A doctor has a patient with very high blood cholesterol levels. Various tests lead to the patient being identified as having familial hypercholesterolemia with a mutation in the LDL receptor gene. The defective LDL receptor gene was cloned from the patient’s DNA and expressed in cultured cells. The following was observed: the mutant LDL receptors were able to bind LDL particles, and these receptors were always localized to the plasma membrane.
Which of the following statements IS the BEST explanation for the data?
a) Binding of LDL particles by the mutant LDL receptors prevented the formation of clathrin-coated pits.
b) Mutant LDL receptors could not bind to clathrin-coated pits.
c) Clathrin-coated vesicles could not form in the cultured cells.
d) Endocytosis of the mutant LDL receptors was followed by degradation in the lysosome.
e) Mutant LDL receptors were no longer phosphorylated.
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13. How is the process of transporting proteins to the nucleus initiated?
The protein destined for the nucleus has a ...
a) N-terminal signal sequence that is bound by a nuclear receptor found on the nuclear envelope.
b) nuclear localization signal that is bound by Ran-GTP.
c) N-terminal signal sequence that binds nucleoporins in the nuclear pore complex.
d) nuclear localization signal that is bound by a cytosolic nuclear import receptor.
e) nuclear export signal that is bound by the Ran binding protein.
14. In COPI vesicular transport, what is the CORRECT order of the following events?
(1) COPI vesicle is uncoated.
(2) Rab-GTP and Rab effectors dock the vesicle.
(3) COPI coated vesicle is formed.
(4) ARF GTPase binds GTP and attaches to the membrane.
(5) v-SNAREs and t-SNAREs interact with each other.
(6) COPI coat proteins are recruited to the cytosolic face of the donor membrane.
(7) Membrane fusion between the vesicle and target membrane occurs.
a) 6, 3, 4, 2, 5, 1, 7
b) 4, 6, 3, 2, 1, 5, 7
c) 6, 4, 3, 5, 2, 7, 1
d) 4, 6, 3, 1, 2, 5, 7
e) 4, 6, 5, 3, 2, 7, 1
15. A scientist clones a gene that encodes protein X. The scientist discovers that protein X contains N-linked oligosaccharides with mannose-6-phophates. The scientist is interested in determining where this glycoprotein is localized in the cell and makes a GFP fusion to express in animal cells. Where do you predict is the final destination for Protein X-GFP?
a) Mainly in the endoplasmic reticulum with some in the Cis-Golgi network.
b) All in the Golgi complex.
c) In the plasma membrane.
d) In the Trans-Golgi network and secretory vesicles.
e) In the lysosomes.
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16. Most soluble and transmembrane proteins sorted to the ER are N-linked glycosylated. Which of the following steps in this process IS FALSE?
a) An N-linked oligosaccharide composed of 14 residues is synthesized directly onto the protein by adding sugars, one at a time, from nucleotide sugar donors.
b) A high-energy pyrophosphate bond provides energy for the glycosylation reaction.
c) The N-linked oligosaccharide is attached to the protein at the Asn-X-Ser/Asn-X-Thr sequence.
d) Three glucoses and one mannose are removed from the N-linked oligosaccharide.
e) The N-linked oligosaccharide is modified by the addition or removal of different sugars.
17. For the Cisternal Maturation model, which of the following statements IS CORRECT?
a) Vesicles bud from the cis Golgi network and fuse with the cis Golgi cisterna.
b) Golgi enzymes in the medial Golgi cisterna are transported by vesicles to the trans Golgi cisterna.
c) The cis Golgi network becomes the new cis Golgi cisterna.
d) Vesicles budding off the cis Golgi cisterna fuse to form the new medial Golgi cisterna.
e) The trans Golgi network forms the new trans Golgi cisterna.
18. For a transmembrane protein with an internal start transfer sequence, what is the role of the adjacent positively charged amino acids?
The positively charged amino acids …
a) are bound by SRP and direct the developing transmembrane protein to the translocator.
b) direct the orientation of the transmembrane protein, and remain on the cytosolic side of the ER membrane.
c) are the signal for the translocator to open laterally and release the transmembrane protein into the ER lipid bilayer.
d) represent the position where the internal start transfer sequence is cleaved following translocation to the ER membrane.
e) direct the orientation of the transmembrane protein, and are translocated to the lumenal side of the ER membrane.
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19. What happens to epidermal growth factor (EGF) receptors following ligand binding and activation?
The activated EGF receptors …
a) accumulate in caveolae and are transported to endosomes for degradation.
b) are collected in COPI-coated vesicles and sorted to the early endosome for recycling.
c) accumulate in clathrin-coated pits for endocytosis, are sorted to the early endosome, and all are packaged in vesicles for recycling to the plasma membrane.
d) are sorted to the trans Golgi network by COPI-coated vesicles.
e) are internalized by clathrin-coated vesicles and transported to the early endosome where most are sorted to the lysosome for degradation.
20. How is Protein Kinase A (PKA) activated?
a) PKA binds to a receptor tyrosine kinase and is phosphorylated by the receptor.
b) cAMP binds to the regulatory subunits and the catalytic subunits are released.
c) G-protein-linked receptor signalling leads to increased cytosolic Ca2+ levels, which in turn activate PKA.
d) PKA binds to inositol phospholipids on the cytosolic face of the plasma membrane leading to activation of its catalytic domain.
e) GTP-bound Ras binds to the N-terminus of PKA and causes a conformational change to activate PKA.
21. A scientist is studying the MAP kinase pathway activated by the FLS2 receptor kinase in plants. The scientist identifies protein Y as a new component in this pathway. Protein Y was found to bind to all the protein kinases in this pathway. What is protein Y?
a) Type I receptor kinase.
b) Grb2 adaptor protein.
c) Protein serine/threonine kinase.
d) Scaffold protein.
e) Protein tyrosine phosphatase.
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22. Binding of thyroid-stimulating hormone to a G-protein-linked receptor leads to activation of a signalling pathway. This pathway results in the expression of the c-fos gene which has a cAMP responsive element in its regulatory region. What is the CORRECT example of signal amplification in this pathway? One …
a) Gα subunit activates multiple adenylyl cyclases.
b) cAMP molecule binds and activates multiple subunits of Protein Kinase A.
c) G-protein-linked receptor activates multiple Gα subunits.
d) Protein Kinase A phosphorylates and activates multiple CREB Binding Proteins (CBPs).
e) molecule of thyroid-stimulating hormone binds and activates multiple G protein-coupled receptors.
23. In receptor tyrosine kinase signalling, what is the CORRECT order of the following events?
(1) Activation of the Sos guanine nucleotide exchange factor.
(2) MAP-kinase goes to the nucleus.
(3) Binding of the Grb2 adaptor protein.
(4) Phosphorylation in the activation loop.
(5) Activation of Raf (MAP-kinase-kinase-kinase).
(6) Receptor dimerization.
(7) Phosphorylation of MAP-kinase.
a) 6, 3, 1, 5, 4, 7, 2
b) 3, 6, 4, 1, 5, 2, 7
c) 6, 1, 3, 5, 4, 7, 2
d) 6, 4, 3, 1, 5, 7, 2
e) 5, 4, 6, 7, 2, 1, 3
24. In the TGF-β signalling pathway, how is Smad2 activated?
a) Smad2 is phosphorylated by the TGF-β Type II receptor.
b) Smad6 binds to the TGF-β receptors, allowing Smad2 to move into the nucleus.
c) The activated TGF-β Type I receptor phosphorylates Smad2.
d) A protein phosphatase dephosphorylates Smad2.
e) Smad4 binds covalently to Smad2.
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25. For ethylene signalling in plants, which of the following steps in this pathway IS FALSE?
a) Ethylene binding leads to activation of the ethylene receptor.
b) A copper cofactor is required for ethylene to bind.
c) The active ethylene receptor leads to activation of CTR1 (MAP-kinase-kinase-kinase).
d) The EIN2 transmembrane protein is activated in the presence of ethylene.
e) Ethylene response genes are activated when the ethylene receptor is shut off.
26. Which one of the following statements concerning dynamic instability is CORRECT?
a) Microtubules depolymerize faster at the end of the filament containing GTP-tubulin.
b) GTP-tubulin ß monomers produce curved protofilaments that are less stable.
c) If GTP hydrolysis proceeds more rapidly than subunit addition, the cap is lost and the microtubule shrinks.
d) The rate constant (kON) is much faster for the plus end of a filament than for the minus end
because the two ends have the same structure.
e) Inside the cell, dynamic instability predominates in microfilaments.
27. Three classes of microtubules are present in the fully formed mitotic spindle. Which
statement concerning the mitotic spindle and associated components is CORRECT?
a) Kinetochore microtubules attach to the telomeres of each chromosome in order to align them at the metaphase plate.
b) Astral microtubules radiate in all directions from the centrosomes and facilitate the
separation of the poles of the cell during interphase.
c) Plus-end-directed motor proteins on overlap microtubules pull the chromosomes toward the centrosome through their attachment at the kinetochore.
d) Inhibition of the APC complex blocks sister chromatid separation at the metaphase
checkpoint.
e) Minus-end directed proteins bound to the cell cortex and astral microtubules push the spindle poles together at the end of anaphase.
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28. Hyaluronic acid is an atypical glycosaminoglycan because
a) it is a highly branched macromolecule.
b) its repeating disaccharide subunits are always the same.
c) its repeating disaccharide subunits are always different.
d) it is the only glycosaminoglycan that is covalently modified by sulfation.
e) its chain length is unusually small relative to other glycosaminoglycans.
29. Which statement regarding collagen or the biosynthesis of a collagen fibre is
CORRECT?
a) Hydroxylation of selected proline and lysine amino acids occurs prior to the completion of pro-α-chain synthesis.
b) Cleavage of the N-terminal and C-terminal propeptides occurs once the procollagen
molecule is transported into a secretory vesicle from the Golgi.
c) Collagen fibres self-assemble into one larger collagen fibril.
d) Four pro-α-chains form a tetrahelical procollagen molecule within the ER/Golgi.
e) Osteogenesis imperfecta is a disease caused by mutations affecting type I collagen.
30. Which one of the following is required for a stable desmosome anchoring junction?
a) The E-cadherin transmembrane proteins of adjacent cells must interact through their extracellular domains in a Ca2+-dependent manner.
b) Intracellular anchoring proteins, such as desmoplakin, must bind to intermediate filaments.
c) Each desmosome must align along the apical region of the cell to form a zonula adherens.
d) Intermediate filaments always are composed of keratin.
e) The tetramer subunits of the intermediate filament must be arranged head-to-tail in order to polarize the filament.
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31. Which of the following types of genomic DNA alterations can convert a proto-oncogene into an oncogene?
a) A loss of function point mutation in the coding region of the gene.
b) A loss of function point mutation in the non-coding promoter region of the gene.
c) Deletion of the entire gene.
d) Multiple copies of the gene caused by errors in DNA replication.
e) All of the above.
32. Which statement regarding apoptosis is FALSE?
a) Bcl-2 activation through a protein kinase B-dependent mechanism facilitates apoptosis. b) Cleavage of the procaspase into an active caspase requires the association of only two
peptide subunits, not including the prodomain.
c) Injured mitochondria and killer T-cells can both cause cell death.
d) Cells dying by apoptosis shrink in size, and their DNA undergoes fragmentation.
e) Active caspase enzymes can cleave other procaspases resulting in an amplification of proteolysis inside the cell.
33. Which statement regarding the critical concentration of a microfilament is CORRECT?
a) The rate of actin polymerization equals the rate of actin depolymerization only at the minus end.
b) The critical concentration of the plus end is equal to the ratio of kADP (kD)
depolymerization to kATP (kT) polymerization.
c) The critical concentration of the minus end is less than the critical concentration of the plus end.
d) The critical concentration at both ends of a filament is not dependent on nucleotide
hydrolysis.
e) The critical concentration is decreased if the lag phase of actin polymerization is eliminated by nucleation of subunits.
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34. Which of the following statements regarding a muscle sarcomere is FALSE?
a) During contraction, binding of ATP to the myosin head causes a conformational change that releases the myosin from the actin.
b) After hydrolysis of the ATP by myosin during the contraction cycle, the ADP + Pi are
quickly removed before the myosin head makes contact with a new actin subunit.
c) The actin filaments in a sarcomere are capped at both ends.
d) The minus ends of the actin filaments within a sarcomere face each other.
e) Actin and myosin filaments in a sarcomere do not shrink during contraction. 35. Which of the following statements regarding gap junctions is CORRECT?
a) The intercellular channels formed by connexons are only homotypic. b) Four connexin proteins make up a single connexon, which can be homomeric or
heteromeric.
c) Gap junctions are large enough to facilitate the transport of proteins between two cells, but not large enough for polysaccharide or nucleic acid transport.
d) The opening and closing of gap junctions can be regulated by changes in pH and Ca2+
concentration inside the cell, but are insensitive to signals from outside the cell.
e) None of the above. 36. The anaphase-promoting complex
(1) blocks the kinase activity of M-Cdk. (2) is constitutively active during all phases of the cell cycle. (3) requires the E1 and E2 enzymes to facilitate ubiquitylation. (4) can activate separase, which cleaves cohesins.
a) 1, 2, 3
b) 1, 3, 4
c) 2, 3
d) 2, 3, 4
e) 1, 2, 4
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37. A loss of function mutation in γ-tubulin is likely to
a) inhibit centrosome localization.
b) inhibit the binding of γ-tubulin to α-tubulin.
c) inhibit the binding of γ-tubulin to β-tubulin.
d) promote dissociation of microtubules from the plus-end.
e) inhibit the association of the minus-end-directed motors with microtubules.
38. You discover a new molecule you suspect acts similar to ciliary dynein. To test this
hypothesis, you treat sperm with trypsin and isolate intact doublet microtubules stripped of all associated proteins. You next incubate the isolated doublet microtubules in vitro with fluorescently labeled γ-tubulin, your new molecule and ATP. Fluorescently labeled tubulin only labels the ends of the microtubules. Which is the most likely observation that will support your hypothesis that the new molecule is similar to dynein? Pairs of fluorescent ends
a) only slide away from each other.
b) only slide towards each other.
c) slide either away from each other or towards each other.
d) don’t move relative to each other.
e) bend towards each other.
39. The rare genetic disease ataxia telangiectasia (AT) is caused by a loss of function defect in one
of the protein kinases that normally phosphorylates and activates p53. Which sequence of events best describes the response to X-ray induced DNA damage by cells with the AT disease?
a) (1) Increased p21 (Cdk-inhibitor) activity; (2) decreased S-Cdk activity.
b) (1) Increased Mdm2-p53 complex formation; (2) increased p53 activity.
c) (1) Increased p53 degradation; (2) increased G1/S-Cdk activity.
d) (1) Increased G1/S-Cdk activity; (2) decreased Rb phosphorylation.
e) (1) Increased APC activity; (2) decreased M-cyclin degradation.
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40. Which of the following statements regarding retinoblastoma is CORRECT?
a) In a genotypically normal individual, an occasional retinal cell that inactivates one Rb gene copy (allele) will become cancerous.
b) In a genotypically normal individual, two distinct retinal cells each of which inactivates
one Rb allele will become cancerous.
c) In a heterozygous (Rb+/-) individual, an occasional retinal cell that inactivates the normal Rb allele will become cancerous.
d) In a homozygous null (Rb-/-) individual, the inactivation of both Rb alleles will cancel each
other out and reduce the chances of developing cancer.
e) The Rb gene is an example of a proto-oncogene. 41. Cell-Cell adhesion can be decreased by
(1) a mutation in vinculin. (2) a mutation in β-catenin. (3) mutations in integrins. (4) absence of Ca2+ in the culture media. (5) antibodies to fibronectin.
a) 1, 2, 4
b) 2, 4, 5
c) 2, 3, 4
d) 1, 4, 5
e) 3, 5
42. Addition of the fimbrin cross-linking protein to actin filaments causes
a) loose packing of the actin filaments, allowing myosin II to interact with actin.
b) a destabilization of microvilli.
c) capping of the plus end of the actin filaments.
d) capping of the minus end of actin filaments.
e) tight packing of the actin filaments, preventing myosin II from interacting with actin.
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43. Late born neurons of the human cerebral cortex
a) migrate past early born neurons and settle in layers 2 to 4.
b) are attracted to the superficial layers by a netrin protein gradient.
c) migrate along the axons of the early born neurons.
d) continue to proliferate as they migrate past the early born neurons.
e) All of the above. 44. Which of the following statements regarding lateral inhibition in Drosophila sensory
bristle development is FALSE?
a) Activated Notch inhibits Delta expression and prevents sensory mother cell differentiation.
b) Numb inhibits Notch and facilitates neuronal differentiation.
c) A loss of function mutation in Notch results in fewer sensory mother cells. d) Numb is used repeatedly during the formation of the socket, shaft, glial, sheath and
neuronal cells.
e) Asymmetrical localization of Numb is controlled, in part, by the planar cell polarity mechanism.
45. Which statement is FALSE?
a) Glycosaminoglycans directly bind to serine residues of core proteins.
b) The heparan sulfate glycosaminoglycan can facilitate FGF signaling.
c) Fibril-associated collagens link fibrillar collagen to the extracellular matrix.
d) Hydroxyprolines increase the capacity of hydrogen bonding in collagen α-chains.
e) Type I collagen is a major extracellular component of bone.
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46. What is a common feature of all three filament systems that make up the cytoskeleton in eukaryotes?
a) Energy gained from hydrolysis of ATP or GTP is needed for polymerization.
b) All three filament systems are required in all cell types.
c) All three filament systems are dynamic.
d) Individual filaments in each of the three systems have identical protein subunits.
e) All three filament systems have identical mechanical properties.
47. Which statement regarding anchoring junctions is CORRECT?
a) Plasma membranes are very strong and anchoring junctions between cells contribute very little additional strength to tissues.
b) The exclusive function of anchoring junctions is to connect the cytoskeleton of one cell to
the cytoskeletons of neighboring cells.
c) Plasma membranes are very flimsy and anchoring junctions between cells contribute a great deal of strength to tissues.
d) Anchoring junctions are the primary mechanism for cell-to-cell communication.
e) Transmembrane adhesion proteins act alone to interconnect cytoskeletons of adjacent cells.
48. A population of asynchronously dividing fibroblast cells were treated with a fluorescent DNA-
binding dye and sorted for DNA content by flow cytometry. Which of the following statements is CORRECT?
a) If 70% of the population had a relative DNA content of 1, then 70% of the cells are in G2. b) If 10% of the population had a relative DNA content between 1 and 2, then S-phase is the
shortest phase of the cell cycle.
c) If 20% of the population had a relative DNA content of 2, then 80% of the cells are in interphase exclusively.
d) If 20% of the population had a relative DNA content of 2, then 20% of the population has
completed M-phase.
e) Flow cytometry cannot tell you anything about what phase of the cell cycle a cell is in.
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49. You are observing a fish skin cell crawling on a flat bed of ECM-coated plastic under a microscope. The cell is moving ~15 µm/sec in a northerly direction (relative to your field of view). Which sequence of events best describes the movement of the cell?
a) (1) Actin polymerization and protrusion of a lamellipodium at the north end of the cell; (2)
formation of integrin-dependent focal adhesions; (3) profilin dependent relaxation of tension at the south end of the cell.
b) (1) Actin polymerization and protrusion of a lamellipodium at the north end of the cell; (2)
formation of cadherin-dependent focal adhesions; (3) myosin II dependent relaxation of tension at the south end of the cell.
c) (1) Actin depolymerization and protrusion of a lamellipodium at the north end of the cell;
(2) formation of integrin-dependent focal adhesions; (3) myosin II dependent relaxation of tension at the south end of the cell.
d) (1) Actin polymerization and protrusion of a lamellipodium at the south end of the cell; (2)
formation of integrin-dependent focal adhesions; (3) myosin II dependent relaxation of tension at the north end of the cell.
e) (1) Actin polymerization and protrusion of a lamellipodium at the north end of the cell; (2)
formation of integrin-dependent focal adhesions; (3) myosin II dependent relaxation of tension at the south end of the cell.
50. Retinal ganglion neurons in the nasal aspect of a zebrafish retina project their axons to
the
a) contralateral posterior optic tectum.
b) ipsilateral posterior optic tectum.
c) contralateral anterior optic tectum.
d) ipsilateral anterior optic tectum.
e) contralateral posterior retina.
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51. Which of the following statements regarding microscopy is CORRECT?
a) A transmission electron microscope will give the highest possible resolution of external cellular structures.
b) The shorter the wavelength of the illumination source, the greater the resolving power of
the microscope. c) The resolving power of a microscope is a function of the minimum size of objects so that
they can be distinguished as separate things. d) The major advantage of differential interference microscopy is that fixation of the cell
preserves the cellular constituents in position and appearance. e) The ocular micrometer is divided into micrometers (µm).
52. Which of the following statements regarding confocal microscopy is CORRECT?
a) Filters must be mounted below the condenser and within the microscope objective. b) It requires ordinary light. c) It takes advantage of the interference effects caused by varying refractive indices of
cellular constituents. d) It has a very shallow depth of field that is created by excluding light from regions out of
the plane of focus. e) One of its major disadvantages is that there are “haloes” around cellular structures.
53. Which of the following cellular structures is the smallest?
a) Plant vacuole.
b) Mitochondrion.
c) Ribosome.
d) Nucleolus.
e) Chloroplast granum.
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54. Which of the following is NOT found in animal cells?
a) Centrioles.
b) Lysosomes.
c) Gap junctions.
d) Peroxisomes.
e) Plasmodesmata.
55. Which of the following statements regarding cell fractionation techniques is CORRECT?
a) During equilibrium sedimentation, the final position of organelles in the centrifuge tube will depend on their size and shape.
b) The velocity sedimentation technique can be used to separate macromolecules containing
heavy isotopes from macromolecules containing lighter isotopes. c) The main purpose of the steep sucrose gradient in the equilibrium sedimentation technique
is to prevent convective mixing. d) During equilibrium sedimentation, cellular components with the highest buoyant density
will be closest to the bottom of the centrifuge tube. e) During velocity sedimentation, slow sedimenting cellular components will be found in the
densest portion of the sucrose gradient. 56. Fluorescein diacetate (FDA) is sometimes used in microscopy. Which of the following
statements concerning this compound is CORRECT?
a) FDA is converted to fluorescein by cell esterases.
b) FDA is a charged derivative of fluorescein that readily crosses the plasma membrane.
c) FDA fluoresces green when exposed to blue light.
d) Dead cells fluoresce when stained with FDA.
e) FDA is used during phase-contrast microscopy.
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57. You perform a Student’s t-test to determine whether two treatment means are significantly different. Your null hypothesis is that there is no difference between the treatments. The critical t-value for the t-distribution of a two-tailed test for your data is 2.31 at P = 0.05. You calculated a t-statistic of 3.05 from your data. Which of the following statements is CORRECT?
a) There is a less than 5% probability that the difference between the means is due to chance
alone; therefore you reject your null hypothesis and conclude that the difference between treatments is significant.
b) There is a less than 5% probability that the difference between the means is due to chance
alone; therefore you accept your null hypothesis and conclude that the difference between treatments is not significant.
c) There is a greater than 5% probability that the difference between the means is due to
chance alone; therefore you reject your null hypothesis and conclude that the difference between treatments is significant.
d) There is a greater than 5% probability that the difference between the means is due to
chance alone; therefore you accept your null hypothesis and conclude that the difference between treatments is not significant.
e) None of the above.
58. Which one of the following statements belongs in the RESULTS section of a primary
paper?
a) Plant cells protect themselves by secreting anti-microbial compounds. b) The experiment was designed to determine the effect of transport inhibitors on cytosolic
calcium ion concentrations. c) Elicitor solution was added to a final concentration of 5 mM. d) Inhibition of proton ATP-powered pumps had no significant effect on cytosolic Ca2+
concentrations, which is consistent with studies in other plant species. e) The effect of the calcium channel blocker was not complete, suggesting that other channels
may be involved in the signal transduction pathway.
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59. Which of the following components of muscle is the smallest?
a) Myofibril.
b) Myofibre.
c) Sarcomere.
d) Myosin filament.
e) Muscle cell.
60. Which of the following decrease in size when a muscle is contracted?
(1) M line (2) Z-disc (3) light band (I band) (4) dark band (A band) (5) Sarcomere (6) actin thin filament
a) 3 and 5
b) 3, 4, 5
c) 1, 5, 6
d) 1, 2, 4, 5
e) 1 and 3
61. You are given a stock solution of 1 M CaCl2 and another stock solution of 100 mM MgCl2.
You need to make 1 mL of a solution with a final concentration of 50 mM CaCl2 and 2 mM MgCl2. How much of each stock and how much water do you need?
a) 50 µl of CaCl2 stock, 20 µl of MgCl2 stock, and 1000 µl of water.
b) 20 µl of CaCl2 stock, 50 µl of MgCl2 stock, and 930 µl of water
c) 50 µl of CaCl2 stock, 20 µl of MgCl2 stock, and 930 µl of water.
d) 50 µl of CaCl2 stock, 2 µl of MgCl2 stock, and 948 µl of water.
e) 2 µl of CaCl2 stock, 50 µl of MgCl2 stock, and 948 µl of water.
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62. Which of the following statements regarding the regulation of muscle contraction by calcium is CORRECT?
a) Binding of calcium ions to the tropomyosin C complex causes troponin to be pulled out of
its normal binding groove on the actin filaments, thereby permitting the binding of the myosin heads to actin.
b) Calcium binds to ATP allowing for ATP hydrolysis so that the myosin head can complete
the power stroke. c) Binding of calcium ions to troponin C allows the Troponin I-T complex to pull
tropomyosin out of its normal binding groove on actin filaments, thereby permitting the binding of the myosin heads to actin.
d) Calcium ions bind to light chain kinase which causes the phosphorylation of actin light
chains and permits binding of the myosin heads to actin. e) Nerve impulses open voltage-gated Ca2+ channels which cause an influx of calcium ions
into the cytosol where they are used as a cofactor to enhance the ATPase activity of myosin heads.
63. Which of the following statements regarding the FRAP technique is CORRECT?
a) One area of the cell is photobleached and the movement of unbleached fluorescent molecules into the bleached area of the cell is monitored.
b) A region of the cell is irradiated to activate the fluorescent proteins in the cell, and the loss
of fluorescence from the bleached region is monitored. c) One area of the cell is repeatedly photobleached while fluorescence is continuously
monitored in the non-bleached areas of the cell. d) Fluorescently labelled molecules diffusing in and out of a small defined focal volume are
measured over time. e) FRAP is based on the fact that the excitation and emission spectra of fluorescent proteins
are identical.
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64. You are interested in determining whether the mobile fraction of protein X in bean cells changes after the cell is exposed to an elicitor. Which of the following describes the BEST experiment to determine this?
a) Transfect cells with DNA coding for protein X fused in frame to DNA coding for GFP. Examine GFP fluorescence in transfected cells before and after addition of the elicitor.
b) Perform immunohistochemistry using an antibody to protein X and use a confocal
microscope to examine fixed cells obtained before and after addition of the elicitor. c) Transfect cells with DNA coding for the promoter region of protein X fused in frame to
DNA coding for GFP. Examine GFP fluorescence in transfected cells before and after addition of the elicitor.
d) Transfect cells with DNA coding for protein X fused in frame to DNA coding for GFP.
Also transfect some cells with DNA coding for just GFP. Examine GFP fluorescence in transfected cells before and after addition of the elicitor.
e) Expose some cells to the elicitor. Perform a co-immunoprecipitation and Western blot on
both cell treatments. Use fluorescently-tagged antibodies made to detect protein X and the elicitor.
65. Which of the following statements regarding the objectives of the study by Escobar et al.
is CORRECT?
The authors wanted to
a) develop a strategy for high-throughput localization of a selected group of expressed proteins in Arabidopsis thaliana.
b) study proteins that were localized to peroxisomes. c) develop a high-throughput screen for localization of random viral DNA-GFP fusion
proteins from Tobacco mosaic virus (TMV). d) develop a high-throughput method to study subcellular localizations of proteins encoded
by random cDNA-GFP fusions. e) develop a stable transformation system to study the localization of out-of-frame cDNA-
GFP fusion proteins.
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66. Which of the following statements regarding the viral vector transformation system used by Escobar et al. is FALSE?
a) T7 polymerase was used to synthesize viral RNA containing cDNA-GFP fusion protein
sequences. b) Infection foci developed and these were examined with a confocal microscope. c) Aluminum oxide dust was used to inoculate plant leaves with the virus. d) Viral particles were assembled by mixing viral RNA with TMV coat protein. e) A particle gun using high pressure helium gas was used to ensure the viral vector
containing the cDNA-GFP fusion protein gene sequences was inserted into the plant cell. 67. With respect to the video that you watched on peroxisome movement in leek and onion
epidermal cells in lab 10, which of the following statements below is CORRECT?
a) These experiments relied upon the co-localization of two fluorescent proteins with identical emission spectra.
b) The inhibitory effect of cytochalasin D on peroxisome movement was permanent since
peroxisomes could not move again, despite washing of the cells. c) Oryzalin and cytochalasin D directly inhibit the function of intermediate filaments. d) Peroxisome movement in plant cells occurs on the same cytoskeletal protein as in animal
cells. e) Peroxisome movement in plants is dependent on actin filaments.
68. In the Drosophila lab, how was the kinesin-ß-galactosidase fusion protein detected in the
oocyte?
a) Blue fluorescent tagged antibodies recognizing kinesin were used.
b) A GFP protein that bound to the kinesin-ß-galactosidase fusion protein was used.
c) X-gal was added and converted to a blue colour by lactase cloned from the lac operon.
d) ß-galactosidase converted a colourless lactose analogue to a blue colour.
e) IPTG was added and converted to a blue colour by ß-galactosidase.
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69. How could you prevent the movement of kinesin in the oocytes that you used in the Drosophila lab?
a) Do not incubate the oocytes in X-gal.
b) Incubate oocytes with high concentrations of phalloidin.
c) Incubate the oocytes with high concentrations of cytochalasin D.
d) Use a particle gun to insert a gene that codes for latrunculin into the oocyte nucleus.
e) Incubate oocytes with high concentrations of colchicine.
70. Why was bleach used to treat the Drosophila eggs?
a) To remove the vitelline membranes.
b) To stimulate formation of germ cells.
c) To dissolve the chorion.
d) To make them more permeable to X-gal.
e) To remove the blastoderm.
71. Immediately following rapid and repeated nuclear division in an early Drosophila
embryo, a series of plasma membranes grow inward from the egg surface and lead to the formation of the
a) follicle cells.
b) syncytial blastoderm.
c) cellular blastoderm.
d) gastrula.
e) vitelline membranes.
72. Which of the following is a function of microtubules?
They a) provide a protective cage for nuclear DNA.
b) form the contractile ring to divide cells.
c) hold epithelial sheets together.
d) bind to actin during muscle contraction.
e) form motile whips.
26
73. Which of the following BEST summarizes the experiments described in the paper on Drosophila Pod-1 by Rothenberg et al.?
The authors
a) moved from general questions to specific ones and performed experiments on simple
systems before performing experiments with complex systems. b) performed biochemical and genetic manipulations on complex systems first, so that they
could extrapolate their findings to other organisms. c) only performed in vitro experiments, since it was critical that appropriate controls be used. d) investigated a protein that was involved in post-translational modification of a coronin
homologue. e) only performed in vivo experiments so that their conclusions could be more realistically
applied to the systems of other organisms. 74. Which of the following statements regarding growth cones in normal developing neurons
is FALSE?
They
a) are enriched with Dpod-1.
b) help drive the directional extension of the axon.
c) contain rhodaminated microtubules.
d) respond to extracellular cues and incorporate these into cytoskeletal changes.
e) usually have filopodia and lamellipodia.
75. Which of the following is a CORRECT conclusion from the studies done by Rothenberg
et al.?
a) Dpod-1 is not homologous to any known protein.
b) Dpod-1 is a cytoskeletal crosslinker and is needed for correct axon guidance.
c) Embryos lacking all Dpod1 could not form filopodia in growth cones.
d) Dpod-1 expression is confined to the epidermis in the stage 12 embryo.
e) Overexpression of Dpod1-GFP in embryos had no effect on neural cell shape.
END OF TEST