Which of the following statements about the structure of microtubules is FALSE? Group of answer choices Microtubules are built from protofilaments that come together to make a hollow structure. The two ends of a protofilament are chemically distinct, with α-tubulin exposed at one end and β-tubulin exposed at the other end. Within a microtubule, all protofilaments are arranged in the same orientation, giving the microtubule structural polarity. α-Tubulin and β-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments.