Editing Cytoskeleton (section)

===Microtubules===
{{main|Microtubule}}
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Microtubules are hollow cylinders about 23&nbsp;nm in diameter (lumen diameter of approximately 15&nbsp;nm), most commonly comprising 13 [[Microtubule|protofilaments]] that, in turn, are polymers of alpha and beta [[tubulin]]. They have a very dynamic behavior, binding [[Guanosine triphosphate|GTP]] for polymerization. They are commonly organized by the [[centrosome]].

In nine triplet sets (star-shaped), they form the [[centrioles]], and in nine doublets oriented about two additional microtubules (wheel-shaped), they form cilia and flagella. The latter formation is commonly referred to as a "9+2" arrangement, wherein each doublet is connected to another by the protein [[dynein]]. As both flagella and cilia are structural components of the cell, and are maintained by microtubules, they can be considered part of the cytoskeleton. There are two types of cilia:&nbsp;motile&nbsp;and&nbsp;non-motile cilia. Cilia are short and more numerous than flagella. The motile cilia have a rhythmic waving or beating motion compared to the non-motile cilia which receive sensory information for the cell; processing signals from the other cells or the fluids surrounding it. Additionally, the microtubules control the beating (movement) of the cilia and flagella.<ref name="auto">{{cite journal |url=https://www.ncbi.nlm.nih.gov/books/NBK21698/| title=Cilia and Flagella: Structure and Movement |first1=Harvey |last1=Lodish |first2=Arnold |last2=Berk |first3=S. Lawrence |last3=Zipursky |first4=Paul |last4=Matsudaira |first5=David |last5=Baltimore |first6=James |last6=Darnell |date=2 May 2018 |access-date=2 May 2018|via=www.ncbi.nlm.nih.gov|url-status=live|archive-url= https://web.archive.org/web/20180502014625/https://www.ncbi.nlm.nih.gov/books/NBK21698/ |archive-date=2 May 2018}}</ref> Also, the dynein arms attached to the microtubules function as the molecular motors. The motion of the cilia and flagella is created by the microtubules sliding past one another, which requires ATP.<ref name="auto"/>
They play key roles in:
* intracellular transport (associated with dyneins and [[kinesin]]s, they transport [[organelles]] like [[mitochondria]] or [[vesicle (biology)|vesicles]]).
* [[File:Bronchiolar area cilia cross-sections 2.jpg|thumb|Cross section diagram through the&nbsp;cilium,&nbsp;showing the “9 + 2” arrangement of microtubules]]the [[axoneme]] of [[cilium|cilia]] and [[flagellum|flagella]].
* the [[mitotic spindle]].
* synthesis of the cell wall in plants.

In addition to the roles described above, Stuart Hameroff and Roger Penrose have proposed that microtubules function in consciousness.<ref>Hameroff, S. and Penrose, R. Physics of Life Reviews 2014, 11, 39-78</ref>