Final answer:
Tubulin is the globular protein that forms hollow tubes by polymerizing into microtubules, which are a key component of the cell's cytoskeleton. Other cytoskeletal proteins like keratin and actin do not form hollow tubes but serve different structural and motility functions in the cell.
Step-by-step explanation:
The globular protein is used to form filaments as an intermediate step to assembly into hollow tubes is tubulin. Specifically, microtubules are composed of α- and β-tubulin protein monomers that polymerize to form these hollow structures. Microfilaments, another component of the cytoskeleton, are composed of polymerized actin monomers, but they do not form hollow tubes. Instead, actin filaments contribute to various cellular movements. Intermediate filaments, which include proteins like keratin, provide structural support and are not involved in forming hollow tubes. Collagen, another protein mentioned, is a structural protein found in the extracellular matrix and does not form the cytoskeletal structures within the cell.
It is important to understand that each cytoskeletal element serves a distinct function within the cell. While intermediate filaments offer tensile strength and resilience to cellular structures, microtubules are essential for maintaining cell shape, cellular transport processes, and cell division. Actin filaments, or microfilaments, enable a range of cellular movements through their dynamic polymerization and depolymerization.