Kinesin and dynein are motor proteins that function with which cytoskeletal element?

• A. Nuclear membrane
• B. Membrane lipids
• C. Microtubules
• D. Lysosomes

Answer: (C)

Kinesin and dynein travel as motor proteins along cytoskeletal tracks to move cargo inside the cell. The tracks they use are microtubules, which are polar structures with a plus end and a minus end. This polarity lets kinesin usually move toward the plus end (often toward the cell periphery) and dynein move toward the minus end (toward the cell body). This system is essential for transporting organelles, vesicles, and other cargo, especially in long cells like neurons where efficient axonal transport relies on microtubules. Other structures listed, such as the nuclear membrane, membrane lipids, or lysosomes, are not the cytoskeletal tracks used by these motor proteins.