Question

Give the exact location of the centrosome.

Answer 1

Hint: Centrosome is an organelle acting as a microtubule-organizing center of animal cells, and also a regulator of cell-cycle progression. The centrosome is assumed to own evolved only within the metazoan lineage of eukaryotic cells. Fungi and plants lack centrosomes and thus use structures apart from MTOCs to arrange their microtubules.

Complete answer: Centrosomes are composed of two centrioles arranged at right-angles to each other. Each centriole is predicated on a nine triplet microtubule assembled in a cartwheel structure containing centrin, cenexin, and tektin.
Centrosomes’ functions:
> Organizing changes to the form of the cytomembrane that allows the membrane to “pinch” in two during cellular division.
> Ensuring that chromosomes are properly distributed to daughter cells by creating and shortening mitotic spindle fibers.
> They serve to direct the movements of microtubules and other cytoskeletal structures and proteins.
> When animal cells want to vary their shapes, complexes of proteins move the cell’s membranes along a network of microtubules which may bend and alter the shape in response to intra- and extra-cellular signals.
Location: Centrosome is found within cytoplasm near the nucleus. It consists of two centrioles — oriented at right angles, embedded during a mass of amorphous material containing proteins. It’s duplicated during the S phase of the cell cycle. Before mitosis, two centrosomes move apart until they're on opposite sides of the nucleus. As mitosis proceeds, microtubules grow out from each centrosome with their plus ends growing toward the metaphase plate.

Note: Centrosomes and Cancer: Cancer cells have quite the conventional number of centrosomes. They are also aneuploid, and considering the role of centrosomes in chromosome movement, it's tempting to think that the 2 phenomena are related. Mutations within tumor suppressor p53 predispose the cell to excess replication of the centrosomes. The hallmark of cancer is uncontrolled mitosis. Vincristine and taxol are used as anticancer drugs. Vincristine, a drug found within the herbaceous plant (a wildflower), binds to tubulin dimers preventing the assembly of microtubules. This halts cells in metaphase of mitosis and Taxol prevents depolymerization of the microtubules of the spindle fiber. This, in turn, stops chromosome movement, and thus prevents the completion of mitosis.