Cytoskeleton

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Only clearly seen in eukaryotes, the cytoskeleton is seen as filaments running through the cytoplasm of a cell. The cytoskeleton is responsible for a cells shape and movement. Other properties include positioning organelles within a cell and directing transport between intracellular compartments. The cytoskeleton is associated with motor proteins which generate movement and allow the cell to be dynamic. The cytoskelton can be sub-divided into three most abundant components; Actin filaments the smallest fibres being up to 7nm in length, Microtubules the largest fibres 25nm in length and lastly Intermediate filaments which the fibres are 10nm in length. 

Recent cytological studies have shown cytoskeletal structures comprising homologues of actin and tubulin to exist in prokaryotes. These skeletal systems often interract with the murein cell wall and contribute to the vast array of cell shapes exhibited by bacteria [1][2].

The Filaments

The filaments throughout the cell are comprised of subunits. Intermediate filaments are a tetramer that consists of two coiled dimers. Microtubules consist of heterodimers of alpha and beta tubulin and these form protofilaments. Whereas actin filaments have globular subunits. These are arranged into a double helix, thus forming F-actin[3].

The intermediate filaments are smaller subunits which are elongated and fiborous unlike actin filaments andmicrotubules which are compact and globular. [4] 

References

  1. Margolin W. (2009) "Review: Sculpting the Bacterial Cell" Current Biology 19(17): R812-R822
  2. Boron, W and Boulpaep, E (2012). Medical Physiology. Updated ed. Philadelphia: Saunders, Elsevier
  3. Boron, W and Boulpaep, E (2012). Medical Physiology. Updated ed. Philadelphia: Saunders, Elsevier
  4. Alberts et al (2008). Molecular Biology of the Cell. 5th ed. New York: Garland Science. 971.
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