Final answer:
Microtubules perform several functions in cells including transport of vesicles, movement of chromosomes, structural support, and movement of mucus out of the lungs.
Step-by-step explanation:
The microtubules perform several important functions in cells, but formation of gap junctions is NOT one of them. Microtubules are involved in the transport of vesicles, such as COPII vesicles carrying secretory proteins, and the movement of chromosomes during mitosis.
They also provide structural support for the cell and are responsible for the movement of mucus out of the lungs by beating rhythmically in ciliated cells.