cytoskeleton

• provides structural architecture for the cell and is involved in many important cellular processes such as: cell motility, cytokinesis, organelle/protein movement, cell adhesion, phagocytosis (endocytosis/exocytosis), development (tissue invagination)
• cytoskeleton is a dynamic structure: breaks down and re-assembles often
• in 20 years skeleton has been rebbuilt
• most cytoskeleton components are polymers of soluble proteins
• rearrangement of the cytoskeleton allows for cell movement and directionality
• three major elements that are polymers (based on size and structure): microfilaments, intermediate filaments, microtubules
• microfilaments: actin fibers (flexible and cross linked)

  • two stranded helical polymers of actin -8nm diameter
• intermediate filaments: several types of proteins (e.g., lamin)

  • polymer rope like fibers that provide mechanical strength - 10nm diameter
• microtubules: tubulin filaments (rigid structural support)

  • long hallow cylinders of polymerized tubulin - 23nm diameter
• all microtubules originate from centrosome
• microtubules form the spindles in mitosis