Cellulose

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Structure and Function

Cellulose is an unbranched polymer of beta-glucose. It is among the most abundant organic compounds in the biosphere. The linkages are called beta-1,4-glycosidic bonds, formed between adjacent D-glucose monomers undergoing condensation reactions. This polymer forms long, straight chains giving it a rigid structure. Because hydrogen bonds are formed between parallel chains, cellulose forms microfibrils[1]  Around 40 cellulose chains combine together, by forming hydrogen bonds, to form a microfibril. [2]  Thus, cellulose is a major component of plant cell walls, giving the cell tensile strength [3].

Plant cells have a very negative water potential, due to many different solutes dissolved within the cytosol. Water, therefore, enters cells from the outside. The cellulose cell wall, however, prevents osmotic lysis; in this state, plant cells are said to be turgid. Turgor pressure is very important for the mechanical rigidity of the cell, and is also vital for expansion during cell growth [4].

Diet

Mammals do not have the cellulases required to digest cellulose and therefore cannot digest vegetable fibres and wood. However, cellulose is an important dietary factor as a fibre component. Insoluble fibres such as cellulose increase the rate that food travels through the large intestine which minimises the exposure of toxins in the diet [5].

References

  1. Berg J., Tymoczko J and Stryer L., 2007. Biochemistry. 7th edition. New York: WH Freeman
  2. Bruce Alberts et al, 2007. Molecular Biology of the Cell. 5th edition. USA: Garland Publishing Inc.
  3. Berg J., Tymoczko J and Stryer L., 2007. Biochemistry. 7th edition. New York: WH Freeman
  4. Bruce Alberts et al, 2007. Molecular Biology of the Cell. 5th edition. USA: Garland Publishing Inc.
  5. Berg J., Tymoczko J., Stryer L., 2007. Biochemistry. 7th edition. New York: WH Freeman
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