The hollow tubes of protein that help maintain the shape of the cell are called microtubules.

Here's why:

* Structure: Microtubules are long, hollow cylinders made up of the protein tubulin.

* Function: They provide structural support, helping to maintain the cell's shape and prevent it from collapsing.

* Other Roles: Microtubules also play crucial roles in:

* Cell division: They form the spindle fibers that separate chromosomes during mitosis and meiosis.

* Organelle movement: They act as tracks for the movement of vesicles and other organelles within the cell.

* Cilia and flagella: They are the primary components of these structures, which are responsible for cell movement.

Let me know if you have any other questions!