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Microtubule and tubulin metrics [1]. Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm [2] and have an inner diameter between 11 and 15 nm. [3]
An aster is a cellular structure shaped like a star, consisting of a centrosome and its associated microtubules during the early stages of mitosis in an animal cell. [1]: 221 Asters do not form during mitosis in plants. Astral rays, composed of microtubules, radiate from the centrosphere and look like a cloud. Astral rays are one variant of ...
Micrograph showing condensed chromosomes in blue, kinetochores in pink, and microtubules in green during metaphase of mitosis. In cell biology, the spindle apparatus is the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells.
[47] [48] A number of polar microtubules find and interact with corresponding polar microtubules from the opposite centrosome to form the mitotic spindle. [49] Although the kinetochore structure and function are not fully understood, it is known that it contains some form of molecular motor. [50]
The microtubule-organizing center (MTOC) is a structure found in eukaryotic cells from which microtubules emerge. MTOCs have two main functions: the organization of eukaryotic flagella and cilia and the organization of the mitotic and meiotic spindle apparatus, which separate the chromosomes during cell division.
The centrosome is thought to have evolved only in the metazoan lineage of eukaryotic cells. [2] Fungi and plants lack centrosomes and therefore use other structures to organize their microtubules. [3] [4] Although the centrosome has a key role in efficient mitosis in animal cells, it is not essential in certain fly and flatworm species. [5] [6] [7]
Microtubules are assembled from dimers of α- and β-tubulin. These subunits are slightly acidic, with an isoelectric point between 5.2 and 5.8. [14] Each has a molecular weight of approximately 50 kDa. [15] To form microtubules, the dimers of α- and β-tubulin bind to GTP and assemble onto the (+) ends of microtubules while in the GTP-bound ...
In 1903, Nikolai K. Koltsov proposed that the shape of cells was determined by a network of tubules that he termed the cytoskeleton. The concept of a protein mosaic that dynamically coordinated cytoplasmic biochemistry was proposed by Rudolph Peters in 1929 [12] while the term (cytosquelette, in French) was first introduced by French embryologist Paul Wintrebert in 1931.