# Cytoskeleton --- The **cytoskeleton** helps maintain the structure of a [[cell]]. It helps cells move around, keep it's shape, and trafficking things around inside the cell. There are three main types of filaments that make up the cytoskeleton, actin filiments, intermediate filiments, and microtubules. These three are distinguashable by their size, structure, and component proteins. **Actin filiments** are the smallest of the main cytoskeletal elements at about 7nm wide. They are a double helix made up of two [[actin|actin]] strands and are polar—meaning they have a + end and a - end. They are particulary used to *resist* tension, or to pull things. They are also used for movement, such as during [[muscle fibers|muscle twitches]], and during [[cell division]]. ![[actin.png]] **Intermediate filaments** are larger than actin but smaller than microtubules ("intermediate", of course), at about 10 nm. They are made from different fibers (such as keratin, lamina...) that are wound into thicker cables. They are particularly used to resist tension and to anchor things like the [[nucleus]] to its position. ![[intermediate filiment.png]] **Microtubules** are the bigest main cytoskeleton element, at about 25 nm. They are made up of α-tubulin and ß-tubulin dimers and useful for resisting compression. They are used during [[cell division]] to pull chromosomes apart. They also provide "tracks" along which different molecules can walk along in order to transport various things around the inside of the cell. For example, **kinesin** can "walk" along the microtubules by hydrolizing ATP. Like actin, there is a - end and a + end. ![[microtubule.png]] ## Image In the image below you can really get a feel for how important the cytoskeleton is to a cell. Actin: Red DNA: Blue Microtubles: Yellow Intermediates: Green ![[cytoskeleton.png]] ___