Of which substance are microtubules made? In which structures and cellular processes do microtubules participate?
Microtubules are made of consecutive dimers of the protein tubulin (every dimer has an alpha and a beta tubulin associated). Microtubules participate in cell division, they are constituents of cilia and flagella and they also form the centrioles.
Cytoskeleton and Cell Movement - Image Diversity: microtubules tubulin