Microtubules are dynamic polymers involved in various cellular processes. Which of the following statements about microtubules is most accurate?
Correct: C
Microtubules are composed of alpha and beta tubulin subunits and originate from microtubule-organizing centers (MTOCs) like the centrosome in animal cells. They serve as tracks for the directed movement of organelles and vesicles by motor proteins such as kinesin (typically moving towards the plus end) and dynein (typically moving towards the minus end). Option A describes microfilaments (actin). Option B describes intermediate filaments, which are generally more stable than microtubules. Option D incorrectly describes treadmilling direction; treadmilling in microtubules typically involves addition at the plus end and disassembly at the minus end, leading to a net shift if not balanced.