• Question: why is our blood blue before oxygen reaches it?

    Asked by to Kate, Kieren, Rowena, Roy on 19 Mar 2014. This question was also asked by .
    • Photo: Roy Adkin

      Roy Adkin answered on 19 Mar 2014:

      Our blood isn’t actually blue…its just the colour of the veins. Human blood and indeed all blood that has iron as the oxygen carrier is red. Red blood cells are red because of hemoglobin which is the molecule that transports oxygen around the body. When oxygen is bound to the iron in the hemoglobin it is red, when it is transporting bicarbonate to the lungs to be converted to CO2 it is slightly orange in colour (but only ever so slightly more orange)…in this case though the bicarbonate ion is bound to the nitrogen atoms in the hemoglobin…
      When blood is spilt you may notice it goes brown…this is because water molecules bind to the iron in the hemoglobin instead of the oxygen or bicarbonate and gives it a rust colour.
      I hope that answers your question 🙂

    • Photo: Rowena Fletcher-Wood

      Rowena Fletcher-Wood answered on 19 Mar 2014:

      Without looking it up to see who is “right”, I’m going to just say what I’ve always heard that is different from what Roy has said!

      That is that haemoglobin, the protein structure that carries oxygen round the body, consists of four quarters that each have an iron centre in them. This iron centre binds to oxygen. When one iron is bound to oxygen, the haemoglobin molecule bends or buckles, which makes it easier for more to bind [This much is definitely true]. The colour part is then that the changed shape of the molecule also changes how it interactives with light and gives colour: blue when straight and red when bent.

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