Chapter 35 Final Review: ID

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  1. P-loop NTPases
    A protein family that includes proteins that play key roles in converting chemical energy into kinetic energy
  2. Myosin
    Moves along filaments of the protein actin; contains two copies each of a heavy chain, an essential light chain, and a regulatory light chain
  3. kinesin
    Has roles in protein, mRNA, and vesicle transport, as well as construction of the mitotic spindle and chromosome segregation; dimers of two polypeptides; role is to carry cargo from the center of the cell to its periphery
  4. dyneins
    Power the motion of cilia and flagella; and a general cytoplasmic dynein contributes to a variety of motions in all cells; enormous with heavy chains; has six sequences encoding AAA subfamily P-loop NTPase domains arrayed along its length, though only four bind nucleotides; important in sliding microtubules relative to one another during the beating of cilia and flagella; and, it carries cargo from the periphery to the cell center
  5. Kd
    The dissociation constant the defines the monomer concentrations at which the polymerization reaction will take place; the polymerization reaction will proceed until the monomer concentration is reduced to the value of Kd; if it is below, the polymerization reaction will not proceed at all; indeed, existing filaments will depolymerize until the monomer concentration reaches the value of Kd; it is the critical concentration
  6. Decorated actin
    A complex that results from treatment of actin filaments with myosin S1 fragments in the absence of ATP; the myosin head domain is in a conformation close to that observed for the nucleotide=free form
  7. Optical trap
    A tool to study motor processes; relies on highly focused laser beams; small beads are caught in the traps and held in place in a solution; and, an actin filament (if studying myosin motion) can be pulled over a slide with other beads that were coated with myosin; adding ATP allows displacement to occur and be measured
  8. Sarcomere
    The functional unit of a muscle cell. Has an A band and a light I band, which alternate regularly; the central region of the A band is the H zone and is less dense. The I band is bisected by a very dense, narrow Z line
  9. Thick filaments
    Consist primarily of myosin; to form these, myosin molecules self-assemble into thick bipolar structures, with the myosin heads protruding at both ends of a bare region in the center; each head rich region associates with two actin filaments, one on each side.
  10. Thin filaments
    Contain actin as well as tropomyosin and troponin complex
  11. Lever arm
    Amplifies small structural changes at the nucleotide-binding site to achieve the 110-angstrom movement along the actin filament that takes place in each ATP hydrolysis cycle; in muscle myosin, it includes the binding sites for two light chains
  12. Dynamic instability
    The addition and dissociation of tubulin subunits; arises from fluctuations in the number of GT+ or GDP=tubulin subunits at the plus end
  13. Run (bacterial motion)
    Counterclockwise rotation of flagella allows filaments to form a coherent bundle favored by the shape of each filamentīƒ  swim smoothly
  14. Tumble (bacterial motion)
    Bundle flies apart because the screw sense does not match the direction of rotation
  15. Biased random walk
    Tumbling more frequently when moving toward lower concentrations of chemoattractants; this motion facilitates net motion toward conditions more favorable to the bacterium
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Chapter 35 Final Review: ID
2014-11-11 15:24:04
Test Three
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