Final answer:
Microtubules are hollow tubes comprising 13 protofilaments of α-tubulin and β-tubulin dimers, with a dynamic plus end and a more stable minus end anchored to centrioles or MTOCs. They are essential for cell shape, transport, and cell division, particularly in forming the mitotic spindle during prophase.
Step-by-step explanation:
Microtubules Structure and Function
Microtubules are integral components of the cell's cytoskeleton, consisting of hollow tubes formed by 13 parallel protofilaments. These protofilaments are composed of polymerized dimers of α-tubulin and β-tubulin. Microtubules are about 25 nm in diameter and play vital roles in maintaining cell shape, cell movement, and cell division. They have two distinct ends: a growing, or plus end (+end), where alpha/beta-tubulin dimers add on, and a minus end (-end), which is typically anchored at the microtubule organizing center (MTOC).
During interphase, microtubules grow out of structures called centrioles in animal cells or a similar MTOC in plant cells. In the lead-up to cell division, they reorganize to form the mitotic spindle, crucial for segregating chromosomes to daughter cells. Microtubules also form the structure of cilia and flagella, aiding in cell motility.
As cells transition into prophase during cell division, centrosomes, which consist of centrioles, begin to separate, initiating microtubule elongation. This gives rise to the mitotic spindle, which is composed of microtubules extending from centrosomes.