Microtubules

Summary

Microtubules are cytoskeleton components that are made of two proteins, α-tubulin and ß-tubulin. They originate from centrosomes and serve three functions. First, they form the mitotic spindle of mitosis. Second, they make up cilia and flagella. Third, In nerve cells, they form a “railroad track” that motor proteins like kinesin and dynein travel on. Microtubules are also dynamic; they frequently lengthen and shorten.

Key Points

• Microtubules
  • Cytoskeletal component
    • provides structural support, helps with cell movement and transport (vesicles, etc.) within the cell
    • Largest cytoskeletal component (diameter ~25 nm)
  • Originate from centrosomes
    • organelle that serves as the main microtubule organizing center (MTOC) of the animal cell
  • Made of α-tubulin and ß-tubulin
    • Dynamically unstable; frequently lengthen and shorten
      • Microtubules are capable of growing and shrinking in order to generate force
  • Function
    • Forms the mitotic spindle
      • Separates chromosomes (disjunction) toward opposite poles during anaphase, via attachment to centromere at kinetochore
      • Microtubule defects can lead to non-disjunction (non-separation of chromosomes in mitosis)
    • Make up cilia
      • Hair-like projections on cell exterior
    • Make up flagella
      • Tail-like projections that move the cell
    • Form a transport track for kinesin and dynein (motor proteins)
      • Helps move vesicles and other compounds around the cell