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39 Cards in this Set
- Front
- Back
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Components of the cytoskeleton
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Microtubules, intermediate filaments, and actin microfilaments
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Functions of the Cytoskeleton
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structural support, cell motility, cell division, translocation of subcellular organelles, regulation of protein synthesis
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T or F: The cytoskeleton is a statis entity
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FALSE
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What support structure is under the plasma membrane? What is this entity composed of?
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The membrane cytoskeleton. It is composed of microfilaments, cross linking proteins and transmembrane proteins.
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Where are microtubules and intermediate filaments located in a cell?
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Distributed throughout the cytoplasm.
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What is the major component of microfilaments?
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Actin
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Size of Actin filaments
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7nm
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Energy source for actin polymerization
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ATP hydrolysis
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3 phases of actin polymerization
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Nucleation, elongation, steady state
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What is required for actin nucleation to initiate?
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3 monomers of Actin bound together to form a nucleation seed
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What is the rate limiting step for polymerization of microfilaments and microtubules?
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Nucleation
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Which side of a microfilament polymer does actin add to?
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Both! The + end is faster growing, though.
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Describe the structure of Actin.
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Globular protein, 41000 molecular weight
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T or F: Actin polymerization also depends on the presence of K+ and Mg++ salts.
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TRUE
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Why is polarity important in a microfilament?
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It is important in structures that produce movement.
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Give 2 examples of actin arrays.
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Thin filaments of contractile muscles. Microvilli
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T or F: Actin filaments generally polymerize in a similar fashion.
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False. Different Actin Binding Proteins generate a host of differing structures.
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What are myosins and what do they do?
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Actin Binding Proteins that produce movement through the hydrolysis of ATP.
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T or F Actin filaments are extremely important for cell motility.
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TRUE
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List the following Actin Polymers in increasing order of stability: Microvilli, Contractile Ring, Lemellipodia, Thin Fillments of Contractile Muscles
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Contractile Ring < Lemellipodia < Microvilli < Contractile Muscle thin filament
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How do myosin and actin work together for muscle contraction?
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Power stroke of myosin when attached to actin. Energy comes from hydrolysis of ATP.
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Microtubule size
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24nm
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What protein makes up microtubules and what do they look like?
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Tubulin, a dimer. Long hollow rod with 13 dimers per turn.
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What provides the energy for microtubule polymerization?
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GTP
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What are MAPs?
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Microtubule Associated Proteins that can stabilize or crosslink the structure.
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T or F: Microtubules are stable, rigid structures.
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False, they are labile.
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What is the MTOC and what does it do?
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Microtubule Organizing Center. Contains two centrioles and forms mitotic spindle apparatus.
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How do microtubules play an important structural role?
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Help maintain the cell's shape.
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What reinforces the shape of dendrides in neurons?
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Microtubules
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What is cilia made of and describe it's structure?
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The core (axoneme) consists of a circle of 9 microtubule doublets (each with a complete and incomplete microtubule). In addition 2 microtules are in the center of the structure.
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How does a cilia move?
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Dyneins located on the completed microtubule reach out to adjacent doublet and "walk". ATP is hydrolized for the motion.
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Flagella vs. Cilia
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Flagella are longer and usually are found one per cell. Mainly for motion while cilia function to move fluids past a surface. Made of the same complex.
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Kinesins vs. Dyneins: Motion along microtubules?
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Kinesins travel away from the nucleus while Dyneins trael toward the nucleus on microtubules.
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What are the major fibers of the mitotic spindle?
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Microtubules
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Size of intermediate filaments
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10nm
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T or F: Intermediate filaments are polar.
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False. Unlike microtubules and actin, they are non-polar.
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T or F: Polymerization of intermediate fibers does not require hydrolysis of ATP or GTP.
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TRUE
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Are intermediate filaments stable or labile?
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They can be either.
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What intermediate filament proteins are in epithelial cells? The membrane cytoskeleton? In muscles?
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Keritins in epithelial. Lamins in the membrane. Desmin in the muscles. Others include vimentin in fibroblasts, spetins in contractile ring, and neurofillaments in glial fibrillary.
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