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Bacteria contain homologs of cytoskeletal filament subunits …
Trieu-ne una: a. except those of the intermediate filaments. b. but these homologs are incapable of nucleotide binding and hydrolysis.
c. that are less diverse in their function relative to their eukaryotic counterparts. d. that can have different functions to those of their eukaryotic counterparts e. that are dispensable for cell growth and proliferation
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Pregunta 2
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In the dendritic networks of actin filaments in lamellipodia, nucleation of actin polymerization is mostly performed by …
Trieu-ne una: a. ERM proteins b. WASp proteins c. Arp2/3 complex d. WAVE proteins
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Pregunta 3
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In the polymerization in vitro of actin filaments and microtubules from their subunits, what does the “lag phase” correspond to?
Trieu-ne una: a. Nucleation The lag phase corresponds to the rate-limiting nucleation step. If this step is bypassed by introduction of preformed filament seeds, the lag phase disappears.
b. Reaching steady state c. Nucleotide exchange d. ATP or GTP hydrolysis e. Treadmilling
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Pregunta 4
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If the concentration of free subunits is C, under which condition does the growth of a cytoskeletal filament proceed spontaneously?
Trieu-ne una: a. C > 1/kon b. C < 1/koff c. C > kon/koff d. C > koff/kon Cc = koff/kon. At concentrations of monomers C > Cc, the free-energy change for polymerization is negative and growth can proceed spontaneously
e. C > Cc×kon/koff
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Pregunta 5
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The actin-nucleating protein formin has flexible “whiskers” containing binding sites that help recruit actin subunits in order to enhance polymerization by this protein. What protein would you expect to bind to these sites?
Trieu-ne una: a. Thymosin b. Profilin Profilin competes with thymosin for the binding of actin subunits, but unlike thymosin, it does not prevent polymerization. Recruitment of profilin–actin therefore facilitates the rapid formin-mediated actin polymerization.
c. Cofilin d. Gelsolin e. Tropomodulin
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Pregunta 6
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Which of the following actin-binding proteins cannot bind to the same actin filament simultaneously?
Trieu-ne una:
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Cofilin binds preferentially to ADP-containing actin filaments rather than to ATP- containing filaments. Consequently, this protein …
Trieu-ne una: a. competes with profilin for actin binding b. binds to older actin filaments c. binds to the plus end of actin filaments d. stabilizes actin filaments e. all the answers are correct
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Pregunta 10
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The pathogen Listeria monocytogenes can hijack (segrest) the actin cytoskeleton in human cells and spread inside the host. Indicate true (T) and false (F) statements below about this phenomenon. Your answer would be a four-letter string composed of letters T and F only; e.g. TTFF. The movement can be reconstituted in vitro by placing the bacteria in a mixture of actin, formin, gelsolin, and capping protein. Cofilin counteracts the movement by depolymerizing actin filaments. The actin filaments grow with their minus ends pointed toward the bacterium. The movement depends on myosin activity to transport the bacteria on the actin filaments.
Trieu-ne una: a. FFTF b. FFFT c. FTFT d. TTFF e. FFFF
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