Bio exam 4 part 2

  1. how neutrophils/ amoeba move
    • actin assembly in the front of the leading edge
    • contract actin in the back of the cell using myosin and it pulls the back of the cell forward
  2. filopodium
    skinny projections, short, bundles of parallel actin filaments
  3. how are filopodium made
    • come from the branched Arp2/3-scar complex in the edge of cell
    • bundling proteins come to bundle them together
    • they start small and they protrude and start small and grow larger
    • cell moves as filopodium
  4. structure of microvilli in epithelial cells
    specialized filopodium
  5. what causes vertebrate sperm to move
    motile due to single whip actin flagella
  6. Bacterium flagellum
    • produced from protein flagellin
    • 1-100s of flagella
    • each is connected to rotary motors
    • rotary motor is powered by proton gradient across membrane
    • causes cells to swim rapidly
  7. how does bacterium flagellum swim
    • swim toward food in straight lines, chemical gradient
    • they tumble
    • decision to swim or tumble depends on rotation direction of motors
    • when all rotors rotate in the same direction they bundle together
    • when they all switch, the bundle becomes unraveled
  8. limulus-horse shoe crab sperm
    • scruin and actosome and actin
    • actin filaments held together by scruin
    • when fertilized scruin dissociates from actin and causes actin to polymerize and actosome to stretch
  9. Thyone Seaslug sperm
    • initially high actin monomer concentration
    • when fertilized actin polymerizes and stretches the actosome
  10. Dictyostelium slime mold
    • a lot bigger than bacteria, able to detech chemical gradient from front and back of cell of cAMP.
    • receptors bind and detect cAMP around the cell
    • signal amplifies and turns on Rho family GTPases and result in actin polymerization
  11. what govern axon growth during neuronal development
    netrins provide long-range guidance for growth cones for cells that possess netrin receptor
  12. Bulk brute force motility
    • amoeba proteus (very large cell)
    • uses actin/myosin contractions
    • most of cell is actin
    • cytoplasm in contraction area shoots out
  13. Characteristics of Major sperm protein (MSP)
    • sperm of nematodes
    • does crawl by amoeboid motility
    • no actin but they have a cytoskeleton
    • MSP is a small globular protein
    • As it dimerizes, orientation is head to head homodimer
    • no polarity
    • only works in the presence of ATP
  14. Major sperm protein (MSP) function
    • MPOP POates tyrosine kinase, sensitive to pH
    • cells can distinguish pH gradient between front and back of cell
    • MPOP bind MFP2-acts like Formin and causes assembly of protein on high pH concentration in front of cell
    • activate MFP1-leads to disassembly at back
  15. structure of muscle
    repeating structure of sarcomere making up many myofibrils
  16. length of a sarcomere
    1 um diameter(look up more accurate size in textbook)
  17. what are sarcomeres comprised of
    actin thin filaments and myosin thick filaments
  18. orientation of actin in sarcomere
    pointed ends near the center M line, Barbed ends on the end near the 2 z lines
  19. function of tropomysin
    • saturates actin filaments, 1 actin filament for every 7 trop monomers
    • regulate protein protein interactions
    • regulate actin-myosin interactions
  20. function of CapZ
    muscle isoform of capping proteins
  21. function of tropomodulin
    • bind cap pointed ends
    • binds actin and binds tropomyosin
  22. function of alpha-actinin
    • at z-line
    • organize thin filaments in sarcomeres
    • forms hexagonal structure of actin/myosin
  23. Size/structure of nebulin
    • ~700 kDa
    • 185 repeats of 35 amino acidsĀ 
    • spans length of 7 nm filament, leads to actin growth to 7 nm filamentĀ 
    • all thin filaments have a nebulin
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Bio exam 4 part 2