Quaternary structures

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A quaternary structure is a protein structure composed of two or more Polypeptide chains. The quaternary structure is held together by a combination of Hydrogen bonds, disulphide bridges and Ionic bonds[1]. They often also contain an inorganic group called a prosthetic group. An example of a quarternary protein that contains the prosthetic Haem group is Haemoglobin[2]. Haemoglobin is composed of two Alpha polypeptide chains and two Beta polypeptide chains, the Haem group contains four Fe2+ ions which oxygen binds to in order for the protein to transport oxygen around the body. As it contains four Fe2+ ions, when it has four Oxygen molecules bound it is known as being saturated and is carrying[3].


  1. http://www.particlesciences.com/news/technical-briefs/2009/protein-structure.html
  2. https://alevelnotes.com/Protein-Structure/61
  3. http://www.thealevelbiologist.co.uk/haemoglobin
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