MCB 252 Exam 3 Practice
Which term best describes the type of mutant allele that was used to study the role of keratin 14 in transgenic mice? A. Recessive B. Dominant C. Dominant negative D. Constitutively active E. A null allele
C. Dominant negative
If you doubled the concentration of actin in this reaction, what would happen to the concentration of free actin at phase C? A. It would drop by half. B. It would double. C. It would stay the same. D. It would increase four-fold. E. It would decrease four-fold.
C. It would stay the same.
Figure X and Y point to different structures. What is the name of the structure labeled Y? A. Endoplasmic reticulum B. Sarcoplasmic reticulum C. T-tubule D. Golgi E. Lysosome
C. T-tubule
You recently discovered that a formin family member is associated with the plus ends of most or all of the actin filaments that are at the leading edge of lamellopodia. Which model of membrane movement by actin polymerization is most supported by your observation? A. The actin flexing model B. The rectified diffusion model C. The model in which actin polymerization results in pushing on a trans-membrane protein D. Both A and B E. All of the above (A, B, and C)
C. The model in which actin polymerization results in pushing on a trans-membrane protein
Match the protein with its role in the sarcomere. Protein: X = nebulin Y = titin Z = Troponin Role in the sarcomere: i = Acts as a spring ii = Binds Ca++, acts on tropomyosin, and allows myosin to access actin iii = Acts as a ruler to specify the length of the actin filaments A. X = i, Y = ii, Z = iii B. X = iii, Y = ii, Z = i C. X = iii, Y = i, Z = ii D. X = ii, Y = iii, Z = i E. X = ii, Y = i, Z = iii
C. X = iii, Y = i, Z = ii
The figure below was discussed in lecture. This figure refers to myosin family members. Which of the two statements below is/are TRUE, and which is/are FALSE? i = Dictyostelium MIA myosin is more closely related to Acanthamoeba HMW myosin than it is to Human brush border MI myosin. ii = Chicken MV myosin is more closely related to Budding yeast Myo4 than it is to Acanthamoeba MII. A. i and ii are both TRUE. B. i is TRUE, and ii is FALSE. C. i is FALSE, and ii is TRUE. D. i and ii are both FALSE.
C. i is FALSE, and ii is TRUE.
Profilin binds to which end of an actin monomer? A. The plus end B. The minus end
A. The plus end
The assay shown below was discussed in lecture. The actin filaments are moving in the direction indicated in the figure. Which end of the actin filament is labeled "X"? A. The plus end B. The minus end C. Cannot tell from the information provided
A. The plus end
You have purified an uncharacterized actin protein found in mouse macrophage (a motile type of blood cell). You start with an in vitro solution of monomers of your purified protein in a buffer that lacks ATP and Mg++. The concentration of your monomers in the solution is 100 µM. You perform two separate experiments on different samples of your actin solution. In the first you add MGT++ and AMPPNP (as the only nucleotide) to your solution and allow it to go to equilibrium. At equilibrium 99% of the actin is F-actin. You repeat the same experiment only this time you add Mg++ and ADP (as the only nucleotide). At equilibrium you find that 90% of the actin is F-actin. What is the critical concentration of the plus end of filaments formed by your newly identified actin? A. 1 µM B. 2 µM C. 5 µM D. 10 µM E. 50 µM
A. 1 µM
From which germ layer does the neural tube form during Xenopus development? A. Ectoderm B. Mesoderm C. Endoderm D. Neuroderm E. Both A and B
A. Ectoderm
In 2008 the Nobel Prize in Chemistry went to the researchers involved in the development of GFP as an experimental tool for visualization of proteins and expression patterns. What is the advantage discussed in lecture of using GFP rather than immunofluorescence? A. GFP allows visualization of living cells and organisms. B. GFP provides a much stronger signal. C. GFP allows the use of a much simpler, less expensive microscope. D. GFP allows visualization of cells in multicellular organisms. E. Both B and C are advantages.
A. GFP allows visualization of living cells and organisms.
A version of the diagram below was shown during our discussion of laser tweezers and optical traps. If the laser beam and bead were initially positioned as shown in the diagram below, what direction would the bead move? A. North B. East C. South D. West E. Cannot determine from the information provided
A. North
. Intermediate filaments are considered equilibrium polymers, as opposed to actin filaments which are best described as steady state filaments. A. TRUE B. FALSE
A. TRUE
As described in lecture, a polyclonal antibody contains many different antibodies, each of which recognizes a distinct epitope on the surface of an antigen. A. TRUE B. FALSE
A. TRUE
As described in lecture, all cytoskeletal polymers are multi-stranded. A. TRUE B. FALSE
A. TRUE
Exon shuffling occurs at the level of DNA in the genome; whereas, splicing occurs at the level of RNA. A. TRUE B. FALSE
A. TRUE
In lecture we discussed an experiment that utilized a plastic bead coated with the ActA protein. What conclusion did we come to based on the results of that experiment? A. That polymerization of actin is sufficient to move a membrane. B. That Myosin V motor heads have a 72nm step size. C. That ATP hydrolysis by actin provides the energy required to move a membrane. D. That stress fibers are involved in moving Listeria. E. That ActA is a motor protein that is necessary for movement of Listeria.
A. That polymerization of actin is sufficient to move a membrane.
You are watching Listeria moving around inside two cells. You inject one cell with phalloidin. What are you most likely to expect to see happen in the injected cell? A. The comet tails will become longer in the injected cell than the non-injected cell. B. The comet tails will become shorter in the injected cell than the non-injected cell. C. The bacteria in the injected cell will move faster than in the non-injected cell. D. The bacteria in the injected cell will stop moving. E. Both B and D are correct.
A. The comet tails will become longer in the injected cell than the non-injected cell.
A version of the figure below was discussed in lecture. Answer the following question based on this figure and our discussion. Ejection of the inorganic phosphate provides the energy needed for myosin motors to undergo the powerstroke. In addition, as described in lecture and shown in this figure, inorganic phosphate is ejected from the leading head just prior to the portion of the figure labeled W. In which conformation is the leading head in the portion of the figure labeled W and X? A. The leading head is in the pre-powerstroke conformation in both W and X. B. The leading head is in the pre-powerstroke conformation in W and the postpowerstroke conformation in X. C. The leading head is in the post-powerstroke conformation in W and the prepowerstroke conformation in X. D. The leading head is in the post-powerstroke conformation in both W and X.
A. The leading head is in the pre-powerstroke conformation in both W and X.
As discussed in lecture, mutations that gave rise to the keratin family of intermediate filaments likely allowed for which major evolutionary transition? A. The transition from animals that only had exoskeletons to animals that had soft exterior parts. B. The transition from lower primates to the emergence of Homo sapiens. C. The transition from animals that only lived in the oceans to terrestrial animals. D. The transition from animals that lacked muscles to the emergence of animals that contained muscles. E. The transition from prokaryotes to the emergence of eukaryotes.
A. The transition from animals that only had exoskeletons to animals that had soft exterior parts
You are carrying out in vitro chemical reactions using an enzyme that produces a deadly cyanide gas when you add the substrate for that enzyme. You have produced a monoclonal antibody and a polyclonal antibody against your cyanide-producing enzyme. Normally when you work with your enzyme you wear protective gear to prevent you from inhaling the deadly gas that is produced. However, today you accidentally add the substrate to the enzyme before you put on your protective gear and rapidly find yourself in a forming cloud of cyanide gas. You start to become weak and realize you need to stop the reaction in order to save your life. Luckily, you have taken MCB 252 and realize that your two tubes of antibodies could potentially help you out. Unfortunately, you only have time to add one of the tubes of antibodies before you are overcome by the gas. Which tube of antibodies would be best to add? A. The tube containing the polyclonal antibody. B. The tube containing the monoclonal antibody. C. Based on our discussion in lecture, it is likely that either one would be equally effective. D. Based on our discussion in lecture, neither one would be expected to have any effect on the reaction and, as a result, you cannot stop the reaction.
A. The tube containing the polyclonal antibody.
Which of the following is/are often properties of protein domains? A. When properly folded, the N- and C- termini often point in opposite directions. B. They are often end coded by adjacent exons with the N-terminal portion of the domain in the upstream exon and the C-terminal portion of the domain in the downstream exon. C. They are often end coded by adjacent exons with the C-terminal portion of the domain in the upstream exon and the N-terminal portion of the domain in the downstream exon. D. Both A and B E. Both A and C
A. When properly folded, the N- and C- termini often point in opposite directions.
Figure Which structure serves as a storage site for Ca++? A. X B. Y C. Z D. All of the above (A, B, and C) E. None of the above
A. X
In lecture we discussed the fact that actin plays a role in phagocytosis. Based on that discussion, do you expect that addition of latrunculin to cells would stop phagocytosis? A. Yes, latrunculin would stop phagocytosis. B. No, latrunculin would not stop phagocytosis.
A. Yes, latrunculin would stop phagocytosis.
As discussed in lecture, there are approximately how many different types of cells in humans? A. 51 B. 210 C. 710 D. 1,710 E. 7,100
B. 210
As described in lecture, Homo sapiens migrated out of Africa before Neanderthals migrated out of Africa. A. TRUE B. FALSE
B. FALSE
As described in lecture, because actin filaments are helical, any motor protein that moves along those filaments must follow a helical path. A. TRUE B. FALSE
B. FALSE
As discussed in lecture, the contractile bundles (sarcomeres) found in muscle cells most likely appeared in evolution before the contractile bundles found in stress fibers. A. TRUE B. FALSE
B. FALSE
In lecture, we discussed the modular construction of some genes and the evolution of genes (and proteins) by the addition of domains. As described in lecture, this process occurs in prokaryotes and eukaryotes. A. TRUE B. FALSE
B. FALSE
Which step in the ATPase cycle of myosin II results in rotation of the head into the "cocked" position? A. Binding of ATP to the myosin head B. Hydrolysis of ATP to ADP + Pi C. Release of Pi from the myosin head D. Release of ADP from the myosin head E. None of the above are correct.
B. Hydrolysis of ATP to ADP + Pi
You have now elected to stand on an Arp2/3 complex. The Arp2/3 complex just nucleated a new actin filament, and that daughter filament has polymerized to add several thousand actin subunits. Now you see that a myosin II molecule (similar to the myosin that drives muscle contraction) has landed on the middle of the daughter filament produced by the Arp2/3 molecule upon which you are standing. What do you see? A. Yikes! Better jump off the Arp2/3 because the myosin is moving towards you very rapidly! B. No worries. The myosin is moving away from you. C. Hard to tell as there is an equal probability that the myosin will move away from the Arp2/3 or towards the Arp2/3. D. Hard to tell as the Arp2/3 complex binds to either end of the actin filament. E. Myosin motors do not move on actin filaments.
B. No worries. The myosin is moving away from you.
Which of the following describes a major function of the intermediate filament cytoskeleton? A. Provides tracks for motor dependent movement of organelles B. Provides mechanical stability to tissues C. Partitions the genetic material during mitosis D. Partitions the cytoplasm at the end of mitosis E. Powers muscle contraction
B. Provides mechanical stability to tissues
What accounts for phase B of the curve? A. Rapid growth as actin filaments are added to individual monomers B. Rapid growth as individual monomers are added to the ends of growing filaments C. Rapid growth as monomers add to monomers D. Rapid growth as actin filaments are added to actin filaments E. Rapid growth as multiple pre-existing filaments attach to each other.
B. Rapid growth as individual monomers are added to the ends of growing filaments
The length of which region of myosin determines the step size? A. The length of the head region B. The length of the lever arm C. The length of the tail D. As discussed in lecture, although we know that different myosin family members take different step sizes, we do not yet have a molecular explanation for how they take different size steps.
B. The length of the lever arm
Congratulations! You finally managed to build a ray gun that allows you to shrink yourself down to the size of a molecule. Like any normal person, your first idea is to stand on top of a 4 formin protein. That formin protein that you are standing on is immobilized on a solid surface. Actin monomers then start to arrive at the formin upon which you are standing. Looking down the filament, what do you see? A. A steady stream of actin subunits moving towards you. B. The minus end of the actin filament is moving away from you. C. The plus end of the actin filament moving away from you. D. Nothing is moving because formins cap the (+) ends of filaments such that they do not grow. E. Nothing is moving because formins cap the (- ) ends of filaments such that they do not grow
B. The minus end of the actin filament is moving away from you.
Which term below most specifically refers to the type of allele that revealed the role of Rac in actin filament formation? A. recessive B. dominant 18 C. dominant negative D. recessive positive
B. dominant 18
Which of the following is correct with regard to the two statements below? i = As described in lecture, the concentration of actin monomers in cells is approximately 100x the critical concentration. ii = As described in lecture, the plus end of a typical actin filament has a higher critical concentration than the minus end. A. Both i and ii are TRUE. B. i is TRUE, and ii is FALSE. C. i is FALSE, and ii is TRUE. D. Both i and ii are FALSE.
B. i is TRUE, and ii is FALSE.
Which of the following is correct with regard to the two statements below? i = Adult stem cells are pluripotent. ii = When a stem cell divides one of the two resulting cells is a stem cell. A. Both i and ii are TRUE. B. i is TRUE, and ii is FALSE. C. i is FALSE, and ii is TRUE. D. Both i and ii are FALSE.
C. i is FALSE, and ii is TRUE.
Which of the following statements is/are TRUE, and which is/are FALSE? i = The majority of different colors of fluorescent proteins used by cell biologist are all naturally occurring proteins that were isolated from different types of aquatic organisms. ii = As described in lecture, when purifying a protein of interest one needs an assay that is specific for that particular protein. A. Both i and ii are TRUE. B. i is TRUE, and ii is FALSE. C. i is FALSE, and ii is TRUE. D. Both i and ii are FALSE.
C. i is FALSE, and ii is TRUE.
You have purified an uncharacterized actin protein found in mouse macrophage (a motile type of blood cell). You start with an in vitro solution of monomers of your purified protein in a buffer that lacks ATP and Mg++. The concentration of your monomers in the solution is 100 µM. You perform two separate experiments on different samples of your actin solution. In the first you add MGT++ and AMPPNP (as the only nucleotide) to your solution and allow it to go to equilibrium. At equilibrium 99% of the actin is F-actin. You repeat the same experiment only this time you add Mg++ and ADP (as the only nucleotide). At equilibrium you find that 90% of the actin is F-actin. What is the critical concentration of the minus end of filaments formed by your newly identified actin? A. 1 µM B. 2 µM C. 5 µM D. 10 µM E. 50 µM
D. 10 µM
The image below was discussed in lecture. What type of cell is shown in this image? A. The image is a schematic representation of any eukaryotic cell. B. The image is a schematic representation of any prokaryotic cell. C. A muscle cell D. A red blood cell E. A cell that is moving in response to a signal
D. A red blood cell
What accounts for phase A of the curve? A. The time required for actin to hydrolyze ATP to ADP B. The time required for the S1 fragment to bind to actin C. The critical concentration of ATP-G-actin D. Actin monomers must assemble to form a nucleus. E. Both A and D are correct.
D. Actin monomers must assemble to form a nucleus.
A muscle fiber is A. an individual muscle cells. B. multinucleate. C. the smallest unit of contraction. D. Both A and B E. All of the above (A, B, and C)
D. Both A and B
In order to determine the structure of a protein by X-ray crystallography you need which of the following? A. The protein of interest needs to be purified. B. You need to know the amino acid sequence of the protein of interest. C. You need to know the approximate shape of the protein from electron microscopy. D. Both A and B E. All of the above (A, B, and C)
D. Both A and B
Some of the humans that migrated out of Africa early in human history interbred with Neanderthals. Some Neanderthal alleles are still retained in the human descendants of those interbreeding events. As discussed in lecture, some of the Neanderthal alleles still retained in modern humans are in gene(s) that effect which property(ies) or protein(s)? A. Skin pigmentation B. Keratins (skin intermediate filaments) C. Sarcomere function D. Both A and B E. All of the above (A, B, and C)
D. Both A and B
UIUC alumnus James Spudich studies hypertrophic cardiomyopathy (HCM). The hearts of people suffering from HCM contract with more average force than the hearts of people who do not have this disease. As a result of the increase force of contraction, the heart wall thickens in patients with HCM which eventually leads to a sudden heart attack and premature 7 death. DNA sequence analysis of more than 400 HCM patients revealed that mutations in cardiac myosin are responsible for this disease in approximately 40% of HCM patients. The vast majority of these mutations cause a single amino acid change in a given patient; however, collectively in the patient population many different amino acids are changed. Jim Spudich analyzed the position of these mutation relative to the structure of the myosin protein. What did he find? A. That many of the mutations were in the region of the head known as the myosin mesa. B. That many of the mutations were in the S2 domain. C. That many of the mutations were in the ATP binding region. D. Both A and B E. All of the above (A, B, and C)
D. Both A and B
Which of the following proteins allows for the arrangement of actin filaments into parallel bundles of filaments? A. α-actinin B. fimbrin C. filamin D. Both A and B E. All of the above (A, B, and C)
D. Both A and B
Bill Brieher's lab here at UIUC identified a protein known as CRMP that promotes actin assembly inside cells. Perhaps you can help us identify the mechanism. The graphs shown below show a series of experiments where we measured the rate of actin polymerization in the presence of varying combinations of CRMP, Arp2/3, and ActA, which is a known activator of the Arp2/3 complex. Given these experiments, which of the following is the most reasonable statement regarding CRMP function with respect to actin assembly? A. CRMP is an actin nucleation factor. B. CRMP is a direct activator of the Arp2/3 complex. C. CRMP inactivates the Arp2/3 complex. D. CRMP promotes actin polymerization in the presence of Arp2/3 and ActA. E. CRMP directly stabilizes actin "minimal seeds" for assembly.
D. CRMP promotes actin polymerization in the presence of Arp2/3 and ActA.
Which term below most accurately identifies the set of three proteins labeled X as indicated by the arrows? A. Adaptins B. Connectins C. Attachins D. ERM family members E. Spectrin, Ankyrin, and Arp1
D. ERM family members
Which of the following does not require one or more motor proteins for movement? A. Muscle contraction B. Contraction of a contractile bundle that is part of a stress fiber C. Cytoplasmic streaming D. Movement of Listeria in the cytoplasm of eukaryotic cells E. All of the above require one or more motor proteins.
D. Movement of Listeria in the cytoplasm of eukaryotic cells
Which property of eukaryotic gene regulatory regions, as discussed in lecture, allowed for the evolution complex regulatory regions? A. That core promoters act over precise distances B. That there are different types of core promoters C. That eukaryotic genes have a regulatory promoter D. That enhancers can act over long distances E. Both A and B are correct.
D. That enhancers can act over long distances
Match the term below with the correct description. i = cdc42 ii = Rho iii = Rac X = This Ras family member is part of the signaling pathway that results in the formation of lamellipodia. Y = This Ras family member is part of the signaling pathway that results in the formation of filopodia. Z = This Ras family member is part of the signaling pathway that results in the formation of stress fibers. A. i = X, ii = Y, iii = Z B. i = X, ii =Z, iii = Y C. i = Y, ii = X, iii = Z D. i = Y, ii = Z, iii = X E. i = Z, ii = X, iii = Y
D. i = Y, ii = Z, iii = X
Match the term below with the correct description. i = transgenics ii = transformation iii = transfection X = When DNA is introduced into cells, and that DNA is only transiently maintained in those cells. Y = When DNA is integrated into a chromosome and maintained in all the cells of a living organism. Z = When DNA is introduced into cells in tissue culture and is stably maintained in that population of cells as a result of the DNA integrating into a chromosome in those cells. A. i = X, ii = Y, iii = Z B. i = X, ii =Z, iii = Y C. i = Y, ii = X, iii = Z D. i = Y, ii = Z, iii = X E. i = Z, ii = X, iii = Y
D. i = Y, ii = Z, iii = X
. In lecture we discussed properties associated with highly conserved proteins. Which of the follow is/are among those properties? A. Conserved proteins are often essential proteins. B. Conserved proteins often interact (bind to) other proteins. C. Conserved proteins often have multiple functions. D. Both A and B E. All of the above (A, B, and C)
E. All of the above (A, B, and C)
In Xenopus laevis, proper tissue development requires which of the following? A. Regulated cell division B. Signaling between cells C. Apoptosis D. Both A and B E. All of the above (A, B, and C)
E. All of the above (A, B, and C)
Which of the following contain actin family members? A. The "hubs" of the cytoskeleton that allow for deformation and reformation of the shape of red blood cells B. At least some chromatin remodeling complexes C. The protein complex that is the target of Listeria ActA protein D. Both A and B E. All of the above (A, B, and C)
E. All of the above (A, B, and C)
Which of the following is/are a property(ies) of a reaction that is at steady state? A. At least one parameter of the reaction remains constant over time. B. At least one parameter of the reaction can vary over time. C. At steady state the reaction requires a continuous input of energy. D. Both A and B E. All of the above (A, B, and C)
E. All of the above (A, B, and C)
Given our discussion of the evolution of intermediate filaments, which of the following is most likely the role of the first family member? A. To provide energy for cell movement 17 B. To act as a roadway for motor proteins C. To provide structural support for the plasma membrane D. To provide structural support the mitochondrial membrane E. To provide structural support for the nuclear membrane
E. To provide structural support for the nuclear membrane
Match the protein with its corresponding activity. Protein: i = thymosin β4 ii = profilin iii = cofilin Activity: X = promotes disassembly of actin filaments Y = sequesters actin monomers Z = is a nucleotide exchange factor for actin A. i = X, ii = Y, iii = Z B. i = X, ii = Z, iii = Y C. i = Y, ii = X, iii = Z D. i = Z, ii = X, iii = Y E. i = Y, ii = Z, iii = X
E. i = Y, ii = Z, iii = X
Match the technique with the goal of that technique. Technique: i = column chromatography 8 ii = X-ray crystallography iii = production of a GFP fusion protein in a living cell Goal: X = determine the structure of a protein Y = determine the sub-cellular localization of a protein Z = purify a protein A. i = X, ii = Y, iii = Z B. i = X, ii = Z, iii = Y C. i = Y, ii = Z, iii = X D. i = Z, ii = Y, iii = X E. i = Z, ii = X, iii = Y
E. i = Z, ii = X, iii = Y