- A Actin
- B Tubulin
- C Myosin
- D Collagen
Correct answer: B. Tubulin
Explanation: Microtubules are hollow tubes made of alpha and beta tubulin protein subunits. They form the cytoskeleton and spindle fibers.
Concept context
Cell theory, prokaryotic vs eukaryotic cells, organelles and their functions. Foundation of all biology.