Cytoskeleton

• What is a tubulin molecule composed of?


  A dimer consisting of two subunits
• How does a microtubule change in length?


  By adding or removing tubulin dimers
• What are the functions of microtubules in the cell?


  They shape and support the cell and serve as tracks for motor proteins
• What role do microtubules play during cell division?


  They are responsible for the separation of chromosomes
• Where do microtubules grow out from in many cells?


  From a centrosome near the nucleus
• What is the function of the centrosome in animal cells?


  It contains a pair of centrioles
• What is the structure of centrioles in animal cells?

  Each has nine triplets of microtubules arranged in a ring
• What happens to centrioles before a cell divides?


  They replicate
• What specialized arrangement of microtubules is responsible for cilia and flagella movement?

  A specific arrangement of microtubules
• How do unicellular eukaryotic organisms move through water?


  They are propelled by cilia and flagella
• How do cilia function in tissue layers?


  They beat to move fluid over the surface of the tissue
• What is the difference between motile cilia and flagella in terms of number and length?


  Motile cilia usually occur in large numbers and are shorter than flagella
• How do flagella and cilia differ in their beating patterns?

  A flagellum has an undulating motion, while cilia have alternating power and recovery strokes
• What is the function of a nonmotile cilium?


  It acts as a signal-receiving “antenna” for the cell
• How do membrane proteins on a primary cilium function?

  They transmit molecular signals from the cell’s environment to its interior
• Why is cilium-based signaling important?


  It is crucial to brain function and embryonic development
• What common structure do motile cilia and flagella share?

  Each has a group of microtubules sheathed in an extension of the plasma membrane
• What is the arrangement of microtubules in motile cilia and flagella?


  Nine doublets of microtubules arranged in a ring with two single microtubules in its center
• What is the pattern of microtubule arrangement found in nearly all eukaryotic flagella and motile cilia?


  The 9+2 pattern
• What are the key functions of the cytoskeleton?


  • Organizes cell structures and activities
  • Provides mechanical support and maintains cell shape
  • Anchors organelles and enzymes
  • Facilitates cell motility and movement
  • Manipulates plasma membrane during phagocytosis
  • Regulates biochemical activities