L7 cytoskeleton

• cytoskeleton role:

  • movement
  • transport molecules
  • normal embryonic development
• 3 main types of fibre:

  1. microfilaments (2 actin chains twisted around each other)
  2. microtubules (constructed from globular proteins tubulins)
  3. intermediate filaments (diverse group of proteins)
• microfilaments are 


  globular actin filaments
• microfilaments have a negative and positive end
• microfilaments function:

  • white blood cell transmigration
  • muscle contraction (interact with myosin)
  • cell movement and migration
  • cell separation during cytokinesis
  • cell shape
  • structural roles- formation of microvilli
• other functions of microfilaments:

  • endo and exocytosis
  • cell junctions
• phalloidin can be used to stain _

  actin
• microtubules are made up of:

  alpha and beta tubulin
• soluble actin monomers polymerize to form insoluble filamentous actin (F actin), which is a _ _ _ helical molecule


  double right-handed
• microtubules function:

  • maintaining cell shape
  • cell movement
  • transport of vesicles
  • separation of chromosomes during cell division
• microtubules structure (and related function):

  • act as tracks for vesicles (and small particles) to move
• positive end of the microtubule is more towards the _ end of the cell

  plasma membrane
• negative end of the microtubule is more towards the _ end of the cell

  nucleus
• motor proteins that interact with the microtubules:

  kinesin and dynein
• importance of motor proteins on microtubules:

  move membrane bound vesicles, proteins and organelles
• kinesins move cargo towards the _ end of the microtubules

  positive
• dyneins transport cargo towards the _ end of microtubules

  negative
• microtubule structure:


  9+2 arrangement

  9 doublets in a ring connected to 2 central microtubules
• cross-linking between outer doublets causes

  flicking (wave-like movement)
• nexin in cross-linking causes:

  no sliding, causing the cilium to bend
• differences between cilia and flagellum

  • cilia are shorter (2-20 micrometres) and more numerous than flagellum (10-200 micrometres)
  • although have same structure
• microtubule structure in cell division:

  9+3 structure (making centrioles)
• intermediate filaments function:

  • maintain cell shape (tension bearing element)
  • anchorage of nucleus and other organelles
• intermediate cell can connect cells together
• types of intermediate filaments:

  • keratin
  • lamin (in the nucleus)
  • vimentin (blood vessels)
  • muscle
  • nervous system (neuron filaments)
• intermediate filaments structure:


  fibrous protein supercoiled into thicker cables