The cytoskeleton is classified as both a muscle of the cell and its skeleton. Within a eukaryotic cell, the cytoskeleton is primarily responsible for the organization and movement (or restriction) of organelles within the cell. The cytoskeleton also plays an essential role in cytokinesis, cell division. a) Microtubules: With a diameter of 25 nanometers, microtubules are made up of polypeptide subunits of the protein Tubulin threaded and stacked together to form hollow straw-shaped filaments. These microtubules made of tubulin will constantly grow and break at each end of the filament, resulting in a faster growing end and a slower end, called plus or minus ends, respectively. Tau protein participates in the formation and stability of microtubules. The minus end of a microtubule is anchored in the Centrosome, which organizes and coordinates the Microtubule. Located next to the nucleus, these centrosomes play an essential role in cytokinesis, allowing microtubules to separate duplicated chromosomes. Shortly after complete division, the microtubule dissociates and disappears again. Microtubules are also found in cilia and flagella and, contrary to popular belief, cilia and flagella are actually not protrusions of the cell membrane. Rather, they are continuations of the membrane itself and are made up of cytoplasm and microtubules. These microtubules are also considered part of the cytoskeleton of cells. Flagella Flagella are long, whip-shaped structures known to propel sperm, made up of 9 + 2 arrangements of microtubules. Cilia Cilia are smaller but more numerous than flagella and consist of 9+2 arrangements of microtubules. Found on the cells lining our trachea, cilia function to sweep away particles...... middle of paper ...... orylation causes Tau proteins to lose their function and quickly dissociate or detach microtubules. Floating freely in the axon in the form of oligomers (proteins made up of a few monomeric subunits), many Tau then began to clump together. Becoming denser over time and because accumulations of Tau proteins are insoluble, they formed neurofibrillary tangles, also called aggregates. Additionally, when the Tau protein separates from the microtubule, it disintegrates because the Tau protein is essential for the structure of microtubules. It is currently assumed that these tangles, or aggregates, so characteristic of the brain cells of people with Alzheimer's disease, are not the main cause of the disease. The destruction of microtubules could however be the main cause of Alzheimer's disease, but active research is being carried out on the subject.