Final Answer:
A microtubule that is quickly growing will have a GTP cap that helps prevent the loss of subunits from its growing end. Stable microtubules are used in cilia and flagella; these microtubules are nucleated from a centrosome and involve a "9 plus two" array of microtubules. The motor protein dynein generates the bending motion in cilia; the lack of this protein can cause Kartagener's syndrome in humans.
Step-by-step explanation:
Microtubules, key components of the cytoskeleton, undergo dynamic instability, a process where they alternate between phases of growth and shrinkage. The rapid growth of a microtubule involves the addition of tubulin subunits to its end. These subunits bind to GTP molecules, forming a GTP cap, which stabilizes the microtubule's growing end and prevents subunit loss. A microtubule's stability is essential in specialized structures like cilia and flagella. They are nucleated from a centrosome, a cellular structure serving as a microtubule organizing center. The arrangement of microtubules in cilia and flagella follows a "9 plus two" pattern, referring to a central pair of microtubules surrounded by nine outer doublets.
The bending motion in cilia is facilitated by dynein, a motor protein that interacts with microtubules and generates the required movement. Kartagener's syndrome, a genetic disorder, can result from the absence or dysfunction of dynein, leading to impaired ciliary motion. This syndrome is characterized by respiratory issues, infertility, and abnormal positioning of internal organs. Understanding the intricate interactions between microtubules, associated proteins like dynein, and their roles in cellular structures provides insights into both normal cellular function and pathological conditions, aiding in the development of targeted therapies and treatments for related disorders.