Lysosomes

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Lysosomes are organelles found in all animal cells[1] and less commonly found in plant cells[2], that consist of hydrolytic digestive enzymes enclosed by a single-layer membrane (vesicle)[3].

Their purpose is to break down substances that are harmful or no longer useful for the cell[4], or even entire organelles[5], and recycle their components for later use by the cell[6]. Lysosymes are present in greater numbers in white blood cells, since they are needed to break down toxic substances and bacteria that have been taken in by endocytosis[7]

The hydrolytic enzymes found within the lysosomes are all produced in the rough endoplasmic reticulum (RER) and transported to the Golgi apparatus for modification[8]. They are then released from the Golgi apparatus inside vesicles[9].

The membrane of lysosomes contain H+ ATPases which actively pump protons from the cytosol into the lumen, using ATP as a source of energy. This retains the internal pH of lysosomes at about 4.5 to 5, providing an acid environment for the optimal activity of hydrolytic enzymes contained within[10].

References  

  1. Davidson M.W., Florida State University, 1995. Cited: 24/11/2016 (Available from: https://micro.magnet.fsu.edu/cells/lysosomes/lysosomes.html)
  2. Sullivan J.A., CELLS Alive!, 1994. Cited: 24/11/2016 (Available from: http://www.cellsalive.com/cells/cell_model.htm)
  3. Davidson M.W., Florida State University, 1995. Cited: 24/11/2016 (Available from: https://micro.magnet.fsu.edu/cells/lysosomes/lysosomes.html)
  4. Davidson M.W., Florida State University, 1995. Cited: 24/11/2016 (Available from: https://micro.magnet.fsu.edu/cells/lysosomes/lysosomes.html)
  5. Alberts B., Johnson A., Lewis J., Morgan D., Raff M., Roberts K., Walter P., ‘Molecular Biology of the Cell’, 6th Edition, New York: Garland Science, Taylor & Francis Group. 2015. Page 642
  6. Davidson M.W., Florida State University, 1995. Cited: 24/11/2016 (Available from: https://micro.magnet.fsu.edu/cells/lysosomes/lysosomes.html)
  7. Davidson M.W., Florida State University, 1995. Cited: 24/11/2016 (Available from: https://micro.magnet.fsu.edu/cells/lysosomes/lysosomes.html)
  8. Davidson M.W., Florida State University, 1995. Cited: 24/11/2016 (Available from: https://micro.magnet.fsu.edu/cells/lysosomes/lysosomes.html)
  9. Davidson M.W., Florida State University, 1995. Cited: 24/11/2016 (Available from: https://micro.magnet.fsu.edu/cells/lysosomes/lysosomes.html)
  10. Alberts et al. Molecular Biology of the Cell. Sixth Edition. pg722-723 New York: Garland Science; 2015.
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