Remodelling the cytoskeleton

• Cytoskeleton


  a network of fibres made from protein that extends the whole way through the cytoplasm.
• What does the cytoskeleton do?


  attached to the cell membrane and gives structure and shape to the cell.
• organelles and the cytoskeleton


  organelles like the nucleus are attached to the cytoskeleton and when organelles or entire cells move, it is the cytoskeleton which is responsible
• Microtubules

  hollow straight rods

  Polymer made from two globular proteins A-tubulin and B-tubulin

  25nm thick
• how is length of the microtubules controlled?


  controlled through the polymerisation (assembly) or depolymerisation (disassembly) of tubulin at the ends of the microtubule
• what is the role of the micrutubule?

  deal with location and movement of membrane-bound organelles and other cells components
• where do microtubules come from?


  microtubules come from the microtubules organising centre (mtoc) -known as the centrosome
• centrioles


  form part of the centrosome and are involved in the organisation of spindle fibres during mitosis
• microtubules in mitosis


  Cell division requires remodelling of the cells microtubules

  Spindle fibres are made of microtubules and control the movement of chromosomes during mitosis and meiosis

  The centrosome is the area of the cell where the microtubules are formed
• Microtubules in cell division

  3 roles;

  1. A star-shaped tuff of microtubules called an aster arises from the centrosome and ensures that cell division apparatus are correctly located.
  2. Some microtubule spindle fibres are attached to kinetochore proteins at the centromere of each chromatid
  3. S some microtubules n the spindle do not attach to chromosomes but attach to other microtubules from the opposite centrosome
• how are chromatids pulled to opposite poles of the cell?

  Chromatids ae separated by depolymerization of microtubules which has the effect of pulling the chromatids to the poles
• when is the highest rate of polymerisation/ depolymersation in a cells life?


  during cell division, polymerisation and depolymerization of microtubules is at a far higher rate than at any other time in the cells life