What is the primary function of tubulin in cells?

Tubulin's primary function in cells is to form the hollow cylinder of microtubules, which are essential components of the cytoskeleton. Microtubules are dynamic structures that play critical roles in maintaining cell shape, enabling intracellular transport, and facilitating cell division through the formation of the mitotic spindle. Tubulin proteins polymerize to create these microtubules, providing the structural framework that supports various cellular processes. This function is crucial for the organization and transport of cellular components, highlighting the importance of tubulin in overall cell function and stability. While the other choices involve different cellular functions, they do not accurately represent the primary role of tubulin in microtubule formation.