Question

When a microtubule is growing, the present end is present as an open sheet to which GTP-dimers are added. A cap of GTP-dimers can often form on the growing microtubules during rapid growth periods. How does this cap?

Answer 1

A GTP-cap forms at the growing plus end of a microtubule during its rapid polymerization phase. This cap stabilizes the microtubule by preventing its disassembly, allowing for the continuous addition of α-tubulin and β-tubulin dimers to the structure.

Step-by-step explanation:

During the rapid growth of microtubules, a GTP-cap forms at the plus end of the structure. The walls of microtubules comprise polymerized dimers of α-tubulin and β-tubulin. This cap maintains stability, allowing the microtubule to grow by the addition of more tubulin subunits in a process that consumes energy, often in the form of GTP.

Microtubules perform a variety of functions within the cell, such as providing support to resist compression, acting as tracks for vesicle transport, and facilitating chromosome separation during cell division. They originate from microtubule organizing centers (MTOCs), like the centrioles found near a cell's nucleus. The rapid polymerization phase of microtubules is characterized by the addition of GTP-tubulin dimers to the growing plus end, which creates a GTP-tubulin cap that protects the microtubule from disassembly. When GTP is hydrolyzed to GDP, the cap can become unstable, leading to depolymerization of the microtubule.