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Although this page (http://evolution.berkeley.edu/evosite/evo101/IIIE5aNotadaptation.shtml) denounces the idea that blood's redness is not an adaptation, I remain inquisitive on the matter since no scientific research has been performed in studying its possible advantages.

Does anyone have any ideas on the advantages of having red blood?

Thank you for your time and effort

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    $\begingroup$ I don't think there is an advantage in blood being red. It is a byproduct of the heme being coordinated in the middle of the heme as the active center. Hemolymph has a copper atom there and is more blue/green due to this fact. $\endgroup$
    – Chris
    Commented Jan 19, 2015 at 22:06
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    $\begingroup$ I think your article explained it quite well. Blood is an adaptation. The color of blood is not; it's a coincidence. $\endgroup$ Commented Jan 19, 2015 at 22:11
  • $\begingroup$ @Chris Thank you for your detailed reply, your chemical background has proved useful here. $\endgroup$
    – Turbo
    Commented Jan 19, 2015 at 22:12
  • $\begingroup$ @anongoodnurse So what should I do with this question? Delete it? $\endgroup$
    – Turbo
    Commented Jan 19, 2015 at 22:12
  • $\begingroup$ Totally up to you. If you want a better answer, you can leave it and see what comes up? $\endgroup$ Commented Jan 19, 2015 at 22:13

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The reason why blood is red is rather simple: It is the iron atom in the middle of the heme, which plays the central part in binding oxygen. Depending on the oxidation state the blood looks either dark or light red. The structure is the following (taken from here):

enter image description here

That the color only depends on the coordinated metal atom is shown by another related molecule, the hemocyanin, which is the oxygen carrying molecule in the hemolymph of insects. It contains copper which is colorless in one oxidation state and blue-green in the other. The function is the same, the color is different.

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  • $\begingroup$ Thank you for your answer but I'm a little confused - weren't there four Fe molecules? $\endgroup$
    – Turbo
    Commented Jan 19, 2015 at 22:27
  • $\begingroup$ This is true for the hemoglobin. This consists of four subunits. Each of these carries one heme with one iron atom. Together you have four hemes in the hemoglobin molecule. $\endgroup$
    – Chris
    Commented Jan 19, 2015 at 22:40
  • $\begingroup$ Ah, I see - so your picture shows one heme and one iron atom $\endgroup$
    – Turbo
    Commented Jan 19, 2015 at 22:41
  • $\begingroup$ Yes, this is clearer this way. $\endgroup$
    – Chris
    Commented Jan 19, 2015 at 22:43
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    $\begingroup$ @CRags You are absolutely right. Thanks for finding this error. $\endgroup$
    – Chris
    Commented Jan 20, 2015 at 7:40

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