Microtubules, intermediate filaments, microfilaments, centrioles and basal bodies.

[mudblood100]

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Can anyone explain them and help me distinguish between them? I have read the section in Cliffs multiple times, but it is just not clicking :/

 

[airstrikee]

In order from thickest to thinnest we have microtubules > intermediate filaments > microfilaments

• Microtubules are a hollow rod that is made up of protein subunits called tubulin. By nature, microtubules continuously polymerize (grow) and depolymerize (shorten). Whether or not they polymerize or depolymerize depends on what is happening in the cell. Microtubules are involved in mitosis, helps maintain the cytoskeleton, and acts as a "highway" for the movement of organelles and vesicles. For example, if a vesicle were to travel from one part of the cell to another, it is assisted by proteins that latch onto the vesicle and walk along the microtubule.
• Intermediate filaments are made up of a variety of proteins such as vimentin, neurofilament, desmin, lamins, etc (i don't think you have to know them all). Intermediate filaments give a much more permanent structure since they don't actively polymerize and depolymerize like microtubules do. Because of this, they are largely involved in mechanical support for the plasma membrane, fixing organelles in place, and give a nucleus its shape by making up the nuclear lamina.
• Microfilaments are made up of the protein actin, so they are also referred to as actin filaments. A microfilament is a double helix of actin and they are heavily involved in things that constantly need to change shape (such as muscle cells), and are also involved in cell motility.

Centrioles and basal bodies are microtubule organizing centers. Remember how I said microtubules continuously polymerize and depolymerize? These MTOCs are major sites of controlled microtubule organization, growth and activity. You can think of them as anchor points for microtubules because these MTOCs help stop microtubule subunits from randomly depolymerizing. Centrioles give rise to the spindle apparatus seen in mitosis, and basal bodies form the base of a flagellum or cilium. The microtubules in a centriole and basal body are organized in a "9+0 array", where 9 triplets of microtubules are arranged in a circle