Microtubules are made up of protein molecules. Chromosomes are pulled apart during mitosis by microtubules. Cilia and flagella are composed of microtubules. Structure Microtubules are composed of proteins which form a tube. They range in length from 200 to nm to 25 micrometers.
Microtubules radiate outward from a point in the cell called the microtubule organizing center.
In animal cells the centrioles are located in this center. Function Microtubules have several known functions in eukaryotic cells. As the cytoskeleton they help maintain the structure and shape of the cell. Second, they play a role in the transport of materials inside the cell. They act as paths along which vesicles containing cell products move.