Exam 2, BIO201, 2004 Form AChoose the one best answer for each question.1. An example of a difference between microtubules (MTs) and microfilaments (MFs) is:A. MTs are seen in the cytoplasm while MFs aren’t B. Some MTs can show cold lability while MFs don’tC. MFs are not polymers while MTs areD. Only MTs have identifiable plus and minus ends.E. MTs can be seen in vivo by immunofluorescence but MFs can’t 2. An example of a fiber that shows dynamic instability is:A. Basal body protofilament B. Intermediate filaments (IFs) in the nuclear laminaC. Cytoplasmic microtubule (MT) in fertilized sea urchin egg mitotic spindleD. Microfilament (MF) in a sarcomereE. Axonemal microtubule in Paramecium cilia3. Which of the following is not an example of the function of microfilaments?A. Scaffolding to provide cell shapeB. “Rails” for intracellular transportC. ATP-dependent cell movement (motility) in conjunction with myosin I.D. Structural support for microvilli and filopodiaE. Flagella movement in eukaryotic sperm4. Nexin bridges connect:A. A tubules to other A tubulesB. A tubules to neighboring B tubulesC. A tubules to the central sheathD. Inner dynein arms to outer dynein armsE. Central microtubules5. Which of the following is not an ATP-dependent motor protein? A. Myosin IB. Ciliary dyneinC. ActinD. KinesinE. Cytoplasmic dynein6. Why were fertilized sea urchin eggs used for reversible cold-lability studies?A. Because they grow and divide at 0-4oC.B. Because the only kind of MTs they have are cytoplasmic MTs C. Because they have so much more MTs for intercellular transport D. Because their mitotic spindles are so big and so easily seen in vivoE. Because they are anisotropic at 2oC.7. Which of the following requires ATP hydrolysis?A. Actin polymerizationB. Anterograde transport of cargo along axons of neuronsC. Protofilament elongationD. Transport of 10nm particles through nuclear poresE. Dissociation of bound myosin from thin filaments in sarcomeres18. SDS-PAGE can separate MAPS from tubulins primarily because:A. MAPS are positively charged and MTs are negativeB. There is high salt in the gel and gel bufferC. MAPS are bigger than tubulinsD. Tubulin is more hydrophobic than MAPSE. MAPS are monomeric while tubulin polymerizes into MTs9. The process of co-translational translocation is best described as:A. Proteins are made on free polysomes as the ribosomes move down the mRNAB. Translation and transcription happening at the same timeC. The way that ribosomal subunits are assembledD. Moving a protein to the nucleus (by way of an NLS) for further modifications E. Moving a nascent protein across the RER membrane as it is being translated10. An example of an MTOC is:A. A centrosomeB. F-actinC. Beta tubulin with GDP boundD. The plus end of a mature (finished) axonemeE. An unfertilized sea urchin egg11. Dyneins, kinesins and myosins are similar in all of the following except:A. They all contain more than one subunitB. They all have cargo binding sites with the same (conserved) amino acid sequence.C. They all have ATP-dependent motors for headsD. They all can be involved in some sort of intracellular transportE. They all can bind to some sort of protein filament12. Actin filaments are:A. Also called intermediate filamentsB. Also called thick filamentsC. Helical polymersD. About 7-8nm longE. Made up of two different types of actin monomers, G-actin and f-actin13. Beta tubulin (-tubulin):A. Is always at the plus end of growing protofilamentsB. Binds gamma tubulin (-tubulin)C. Is the type of tubulin that is closest to an MTOCD. Is where the tails of ciliary dyneins bindE. Is positively charged (at pH=7.0) so it can bind to the negatively charged  (alpha) subunit at pH=7.014. If you used the Weisenburg procedure to purify microtubules (MTs) from fertilized sea urchin eggs, what would happen if you included a protein synthesis inhibitor (like puromycin) during the homogenization step?A. It would greatly decrease the amount of MTs recovered in the final pellet but some kinds of MTs would still be thereB. It should not affect the amount of MTs recoved in the final pellet to any noticeable extentC. It would greatly increase the amount of MTs recovered because of less proteolysisD. It would cause more MTs to appear in the first pellet (P1) than in the second pellet (P2)E. Since MTs are made of protein, there would be no MTs to recover215. If fluorescent-conjugated actin (not the antibody) is injected into cells it can be used to recognize in vivo:A. Growing microtubules only B. All microtubulesC. All microfilamentsD. All intermediate filamentsE. The plus end of growing f-actin16. Which of the following would be least likely to disrupt (cause to depolymerize) cytoplasmic microtubules?A. Triton X-100 B. Incubating them at 1oCC. ColchicineD. 1.0mM CaCl2E. SDS17. Drug X specifically inhibits the ATP hydrolysis activity of axonemal dyneins. Addition of drug Xto cells would be expected to:A. Stop sperm from swimmingB. Stop cell division in all eukaryotic cell typesC. Stop both anterograde and retrograde transport in neuronsD. Stop chromosomal movements during cell division in eukaryotic cellsE. Stop sarcomere contractions in muscle 18. Tubulin was added to a test tube and the extent of polymerization was assayed by light scattering. No light scattering was seen. Which of the following is the most likely explanation?A. The temperature was too low B. No ATP was addedC. No MAPS were addedD. The Ca++ concentration was too lowE. The tubulin had to be made fluorescent to see light scattering19. Of the following, which is the best way to test whether a MAP is really associated with cytoplasmic MTs in vivo?A. Homogenize cells, add fluorescent anti-MAP antibodies and fluorescent anti-tubulin antibodies (with a different color fluor) and see if the colors co-localize (are in the same place) when analyzed by fluorescence microscopy.B. Microinject anti-tubulin antibodies and fluorescent-conjugated MAPs and use electronmicroscopy to see if they bind to each otherC. Isolate MTs by the Weisenburg method and look for the MAPS by SDS-PAGE in the final, low salt pelletD. Microinject fluorescent-conjugated tubulin into live cells, then inject a different coloredanti-MAP antibody. Use fluorescence microscopy. Look to see if the colors co-localizealong similar lines at the growth temperature but not at 2oC.E. Use high salt to see if the MAPS come off of the MTs during centrifugation20. In