Final answer:
Microtubules are small hollow tubes composed of tubulin dimers that play important roles in cells, such as providing rigidity and facilitating cellular movements. They are also the structural elements of flagella, cilia, and centrioles.
Step-by-step explanation:
Microtubules are a class of cytoskeletal elements in biology. They are small hollow tubes composed of tubulin dimers and have a diameter of about 23 nm.
Microtubules play several important roles in cells, including providing rigidity and shape, facilitating cellular movements, serving as tracks for motor proteins, and pulling replicated chromosomes during cell division.
They are also the structural elements of eukaryotic flagella, cilia, and centrioles.