RR Final 3 Microtubules.2

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RR Final 3 Microtubules.2
2013-11-19 20:28:32
Cell Bio

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  1.                                                               i.      first microtubule-associated motor was __, the protein responsible for movement of cilia and flagella
    __: we can manage with only two, one of which is responsible for most transport operations
    • dynein
    • cytoplasmic dynein
  2. Structure of dynein
    •                                                               i.      huge protein composed of two identical heavy chains and a variety of intermediate and light chains
    • 1.       each dynein heavy chain consists of a large globular head with an elongated projection (stalk)
  3. Explain the head of the dynein
    Explain the stalk
    Explain the stem
    • a.       which is an order of magnitude larger than a kinesin head, acts as a force-generating engine
    •    i.      each stalk contains the all-important microtubule-binding site situated at its tip
    • 1.       the longer projection, known as the stem, binds the intermediate and light chains, whose functions are not well defined
  4. 1.       __ consists of a number of distinct modules organized in the shape of a __, making it fundamentally different in both architecture and mode of operation from kinesin and myosin
    • dynein motor domain
    • wheel
  5.                                                               i.      move along a microtubule toward the polymer’s __--opposite that of __
                                                                ii.      present throughout__, but absent in __
    • minus end
    • kinesins
    •  animal kingdom
    • higher plants
  6. Roles
    • 1.       as a force-generating agent in positioning the spindle and moving chromosomes during mitosis
    • 2.       as a minus-end directed microtubular motor with a role in positioning the centrosome and Golgi complex and moving organelles, vesicles, and particles through the cytoplasm
  7.                                                               i.      in nerve cells, cytoplasmic dynein has been implicated in the __ of membranous organelles and the __ of microtubules
                                                                ii.      in fibroblasts and other nonneural cells, cytoplasmic dynein is thought to do what?
    • retrograde movement
    • anterograde movement
    • transport membranous organelles from peripheral locations toward the center of the cell
  8. 1.       __-driven cargo includes endosomes and lysosomes, ER-derived vesicles heading toward the Golgi complex, RNA molecules, and the HIV virus which is transported to the nucleus of an infected cell
  9.                                                               i.      __ does not interact directly with membrane- bounded cargo but requires an __—most often the multisubunit protein __
    __also regulates dynein activity and help bind the __to the microtubule, which increases __
    • cytoplasmic dynein
    • intervening adaptor
    • dynactin
    • dynactin 
    • motor protein 
    • processivity
  10.                                                               i.      __ and __ move similar materials in opposite directions over the same railway network
    1.       individual organelles may find __ and __simultaneously, which endows these organelles with the capability to do what?
    • kinesins and cytoplasmic dynein 
    • kinesin and dynein 
    • move in opposite directions depending on conditions
  11. a.       it is not clear how the activity of opposing motors is regulated, but in vitro observations have shown that two opposing motor may engage in a type of __, causing the object to which they are attached to __

    myosin also present on some of these organelles, which provides the opportunity for the organelles to __ as well as microtubules
    • tug-of-war
    • move back and forth along the microtubule
    • move along actin filaments
  12. a.        MTOCs
                                                                  i.      the function of a microtubule depends on __ and __
                                                                ii.      when studied in vitro, the assembly of microtubules from __occurs in two distinct phases: what are they?
    • location and orientation
    • αβ-tubulin dimers
    • a slow phase of nucleation, in which a small portion of the microtubule is initially formed, and a much more rapid phase of elongation
  13. 1.       __of microtubules takes place rapidly inside a cell, where it occurs in association with a variety of specialized structures called __

    a.       the best studied is the __
    • nucleation 
    • microtubule-organizing centers (or MTOCs)
    • centrosome
  14.                                                               i.      in animal cells, the microtubules of the cytoskeleton are typically nucleated by the __, a complex structure that contains two __surrounded by __
    • centrosome
    • barrel-shaped centrioles 
    • amorphous, electron-dense pericentriolar material (or PCM)
  15. 1.       __are cylindrical structures about 0.2 micrometers in diameter and twoice as long; contain nine evenly spaced fibrils, each of which appears in cross section as a __

    a.       only the A is a complete __and is connected to the __ by a __
    • centrioles 
    • band of three microtubules, designated A, B, and C tubules
    • microtubule 
    • center of the centrioles by a radial spoke
  16. a.       the three microtubules of each triplet are arranged in a pattern that gives a centrioles a characteristic __appearance
                                                                                                                                          i.      centrioles are nearly always found in __, with the members situated at __ to one another
    2.       __of isolated centrosomes with 1.0 M KI removes about 90% of the protein of the __, leaving behind a spaghetti-like scaffold of insoluble fibers
    • pinwheel 
    • pairs
    • right angles
    • extraction 
    • PCM
  17.                                                               i.      the centrosome is the major site of __ in animal cells and typically remains at the center of the cell’s __

    • microtubule initiation
    • microtubular network
  18.                                                               i.      early experiment demonstrating role of centrosome in initiation and orgnanizaiotn of microtubular cytoskeleton
    1.       the microtubules of a cultured animal cell were first __by incubating the cells in __, a drug that binds to tubulin subunits and blocks their use by the cell
    2.       __ was then monitored by removing the chemical, __ aat various time intervals, and treating the __with __
    • depolymerized 
    • colcemid
    • microtubule reassembly
    • fixing cells
    • fixed cells 
    • fluorescent anti-tubulin antibodies
  19. 1.       within a few minutes after removal of the inhibiting conditions, __ are seen in the cytoplasm of the cell
    a.       within 15 to 30 minutes, the number of labeled __radiating out of these __increases dramatically
    • one or two bright fluorescent spots
    • filaments 
    • foci
  20. a.       when these same cells are sectioned and examined in the electron microscope, the newly formed microtubules are found to __
    b.      the microtubules do not actually __and make contact with the __, but terminate in the __that resides at the __ 
                                                                                                                                          i.      it is this material that initiates __ 
    • radiate outward from a centrosome
    • penetrate into the centrosome 
    • centrioles
    • dense PCM 
    • centrosome periphery
    • formation of microtubules
  21. 1.       although __are not directly involved in __, they play a role in recruiting the surrounding __during __ and in the general process of __
    • centrioles 
    • microtubule nucleation
    • PCM 
    • assembly of the centrosome
    • centrosome duplication
  22.                                                               i.      centrosomes are sites of __
    1.       the polarity of these microtubules is always the same: what?
    • microtubule nucleation
    • the minus end is associated with the centrosome and the plus end is situated at the opposite tip
  23. a.       thus, even though microtubules are nucleated at the __, they are elongated at the __ of the polymer
                                                                                                                                          i.      the growing end of a microtubule may contain a host of __ that help attach the microtubule to a particular target, such as an endosomes or Golgi cistern in an Interphase cell or a condensed chromosome in a mitotic cell
    • MTOC (microtubule organizing center)
    • opposite end
    • specific proteins
  24.                                                               i.      the fraction of microtoubles that remain associated with the __is highly variable from one cell type to another
    1.       the centrosome of a nonpolarized cell is typically situated near __ and tends to __
    • centrosome 
    • the center of the cell
    • remain associated with the minus ends of a large number of microtubules
  25. 1.       in contrast, many of the microtubules in a polarized epithelial cell are __by their __ at dispersed sites near the __of the cell as their __ extend toward the cell’s __
                                                                ii.      similarly, the axon of a nerve cell contains large numbers of microtubules that have no association with the __, which is located in the __
    • anchored 
    • minus ends
    • apical end 
    • plus ends
    • basal surface
    • centrosome
    • neuron’s cell body
  26. 1.       many of these axonal microtubules are thought to form in conjunction with the __, but are then __from the __and transported into the axon by motor proteins
    certain animal cells lack __entirely, but can still form complex microtubular structures such as the meiotic spindle
    • centrosome
    • severed
    • MTOC 
    • centrosomes