Card Set Information

2012-10-20 14:16:02

network of fibers extending through cytoplasm
Show Answers:

  1. Functions
    • 1) organize cell structure/ activities
    • 2) mechanical support to cell/ maintain shape
    • 3) cell motility
    • 4) manipulates plasma membrane, making it bend inward to form food vacuoles or other phagocytic vesicles
    • 5) cytoplasmic streaming
  2. Explain how the cytoskeleton gives mechanical support.
    • strength and resilience are based on architecture.
    • 1) It is stabilitzed by a balance between elements' opposing forces.
    • 2) Provides anchorage
    • 3) can be quickly dismantled and reassembled in new location.
  3. Cell motility

    a.      requires __
                                                                                                                                          i.      __ and __ work together with membrane molecules to allow whole cells to move along __outside the cell
    • motor proteins
    • cytoskeletal elements
    • motor proteins
    • fibers
  4. Motor proteins:
    • 1) bend flagella and cilia by gripping microtubules within those organelles and sliding them against one another; this also occurs in microfilaments, which cause contraction of muscle cells
    • 3) motor protein feet walk to their destinations along cytoskeletal track
  5. Types
    • microtubules
    • microfilaments
    • intermediate filaments
  6. Microtubules
    a. Wall of hollow tube= __protein
    - i. Each __ protein is a __, made up of two subunits
    -- 1. Two slightly different __
    ----- i. grow in length by adding __
    -- 2. can be disassembled and reassembled elsewhere
    b. two ends are slightly __ 
    • tubulin x2
    • dimer
    • polypeptides: α- tubulin and β- tubulin
    • tubulin dimers
    • different: one end accumulates/ releases at higher rate (plus end)
  7. Microtubules functions:
    • i.      Shape and support
    • ii.      Serve as tracks along which organelles can move
    • iii.      Involved in separation of chromosomes during cell division
  8. a.      __: a region near the nucleus; “__”
                                                                                                                                          i.      __ grow out from this, which function as: ___

                                                                                                                                        ii.      Pair of __ within
    1.      __
    2.      Replicate before __
    • Centrosomes
    • microtubule-organizing center
    • Microtubules
    • compressioin-resisting girders of the cytoskeleton
    • centrioles
    • Nine sets of triplet microtubules attached in a ring
    • division
  9. Microtubules are responsible for __.
    beating of flagella and cilia, micrtotubule-containing extensions that project from some cells
  10. Explain flagella and cilia.
    • i. Propelled through water by these that act as locomotor appendages
    • ii. When held in place: move fluid over surface
  11. Motile Cilia
    • occur in large numbers on cell surface 
    • ----- work like oars, with alternating power and recovery strokes generating force in direction perpendicular to cilium's axis 
    • ----- can act as antenna for cell (only one per cell/ transmit molecular signals from cell's environment to interior, triggering signaling pathways that lead to changes in cell activities)
  12. Flagella
    • same diameter as cilia, but longer; usually one or two 
    • undulating motion that generates force in same direction as axi
  13. Similar structure of flagella and cilia
    1. Group of __sheathed in extension of plasma membrane
    a. __ of microtubules arranged in ring; center are__
       i. “__” pattern
       ii. Nonmotile: __, lacking central pair of microtubules
    b. Microtubule assembly anchored by __, with microtubule triplets in ”__” pattern
    • microtubules
    • Nine doublets
    •  two single microtubules
    • 9+2
    • 9+0
    • basal body
    • 9+0
  14. Proteins
    1. Flexible __ proteins, evenly spaced along length of cilium or flagellum, connect outer __to each other and to two __
    --- a. Each outer doublet also has pairs of protruding proteins spaced along its length and reaching toward the neighboring doublet
    -------- i. These are large motor proteins called __, responsible for __ of organelle and performs movements by __, provided by __.
    • cross-linking
    • doublets
    • central microtubules
    • dyneins
    • bending movements 
    • changes in shape of protein
    • ATP
  15. 2. Dyneins
    a. Resembles walking how?
    b. Need __to prevent sliding past each other
         i. Held in place by __ just inside outer doublets and by __, etc.
         ii. Cause doublets to __
    • Two feet that walk along microtubule of adjacent doublet, one foot maintaining contact while the other releases and reattaches one step farther along microtubule
    • restraints
    • cross-linking proteins
    • radial spokes
    • curve
  16. Microfilaments
    a. Also called __filaments because built from __, a globular protein
        i. Twisted double chain of __
    b. Can form __ when certain proteins bind along side of actin filament and allow new filament to extend as __
    • actin x2
    • actin subunits
    • structural networks
    • branch
  17. Function of microfilament
    • i. Bear tension
    • ii. 3D network formed by microfilaments just inside plasma membrane helps support cell shape
    •      1. This give outer cytoplasmic layer of cell, called the cortex, the semisolid consistency of a gel, in contrast withthe more fluid state of the interior cytoplasm
    • iii. in animal cells specialized for transport across membrane, microfilaments make up core of microvillii
    • v. cell motility
  18. Explain microfilament cell motility.
    • 1. contractile apparatus of muscle cells
    • 2.      actin filaments arranged parallel along length of muscle, interdigitated with thicker filaments made of myosin
    • a.      acts as motor proteins by means of projections that walk along the actin filaments
    • b.      contraction results from actin and myosin sliding past one another
    •                                                                                                                                                                                                               i.      also causes amoeboid movement
    •                                                                                                                                                                                                             ii.      cleavage furrow
  19. Microfilaments in amoebas
    1. amoeba crawls along surface by extending __, cellular extensions, and moving toward them
    a. extend by assembly of __ into microfilament networks that convert cytoplasm from a __to a __inside these cell projections
    i. __ proteins make strong attachments to the “road”
    ii. interaction of microfilaments with myosin near cell’s trailing end causes __of region, __its cell-surface attachments and pulling it forward toward the __
    • pseudopodia
    • actin subunits
    • sol
    • gel
    • cell surface
    • contraction
    • loosening
    • pseudopodia
  20. Microfilaments in plant cells
    1. both __ and __brought about by actin involved in __, a circular flow of cytoplasm within cells;
    What does it do?
    • actin-myosin interactions
    • sol-gel transfomraiton
    • cytoplasmic streaming
    • speeds distribution of materials within cell
  21. Intermediate Filaments
    a. Named for __
    b. Diverse class of cytoskeletal elements
    ---i. Contstructed from particular molecular subunit belonging to family of proteins whose members include __, unlike microtubules and microfilaments, which are consistent
    c. Functions
    d. More permanent fixtures
    ---1. Persist __
             1) where is it located?
             2) Creates a cage in which the __ sits
    • diameter
    • keratins
    • bear tension
    • even after death
    • outer layer of skin
    • nucleus
  22. Extracellular components:
    cell wall of plants
  23. Function of cell wall of plants
    • protects
    • maintains shape
    • prevents excessive uptake of water
    • strong walls hold plant up againast gravity
  24. Structure of cell wall of plants
    • thicker than plasma membranes
    • chemical composition varies
    • cellulose synthase makes cellulose to be secreted and embedded in matrix of extracellular space
  25. Levels of cell wall of plants
    • Primary Cell wall
    • middle lamella
    • secondary cell wall
  26. Primary Cell wall
    • first secreted
    • thin and flexible
    • cellulose fibrils oriented at right angles to direction of cell expansions
    • --- microtubules guide cellulose synthase as it synthesizes and deposits cellulose fibrils
  27. Middle lamella
    • i. Thin layer rich in pectin (sticky polysaccharides)
    • ii. Glues adjacent cells together
  28. Secondary Cell Wall
    • i. Between plasma membrane and primary wall
    • ii. Strong and durable matrix
    • 1. Protection
    • 2. Support