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#91401
01/10/2003 9:13 AM
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Joined: Sep 2001
Posts: 6,296
Carpal Tunnel
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Carpal Tunnel
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#91402
01/10/2003 10:37 AM
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Joined: Dec 2002
Posts: 122
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at first i had doubts about it, but then i realised that i.e. hemocyanin which contains copper is achromic when in its reduced form and blue when oxygenated. chlorokruorin is green (and contains chlorine - the same effect as in chloroplasts), aso. therefore it would be logical if it were iron what gives hemoglobin its red color - the heme is obviously the thing which causes it, and searching through this structure only iron seems to be proper answer. of course i might be wrong  must correct myself:
when i wrote about oxygenated form of hemocyanin i meant its oxidised form. i still don't really well know chemistry vocabulary.
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#91403
01/10/2003 12:13 PM
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Joined: Sep 2001
Posts: 6,296
Carpal Tunnel
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Carpal Tunnel
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#91404
01/10/2003 11:23 PM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
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Dear WW: the blue of "blueprints" is a ferricyanide. But the color of the pigment is not from
the iron alone. For instance simple iron compounds have very little color. It takes a big molecule
to absorb the right wavelengths of llight to give color. And the majority of dyes and pigments
do not have any metal in them. Remember how many colors come from "coal tar"?
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#91405
01/10/2003 11:38 PM
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Joined: Sep 2001
Posts: 6,296
Carpal Tunnel
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Carpal Tunnel
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#91406
01/10/2003 11:57 PM
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Joined: Sep 2001
Posts: 6,296
Carpal Tunnel
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Carpal Tunnel
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#91407
01/11/2003 1:02 AM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
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Dear WW: To bad Alex, doc_comfort, and wofahullicodoc are not available to discuss this.
They know more about this than I ever did, and I have forgotten most of what I once knew.
But I doubt that the oxygen is binding directly to the iron. Oxygen has a valence of two,
and I'll bet all of the iron's valene is already involved. So while the iron is indispensible, it
just makes possible a huge molecule that can bind oxygen loosely enough
to give up in the tissues where it is needed, and then take up CO2 to take back to the lungs.
Hemoglobin is a very complicated molecule. And its size and complexity have more to do with
its color than the iron does. When hemoglobin is broken up, the iron is recycled, and the residue
give the orange-yellow-brown color to bile and stools. The color change is mostly due to smaller
molecule size.
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#91409
01/11/2003 9:34 AM
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Joined: Sep 2001
Posts: 6,296
Carpal Tunnel
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Carpal Tunnel
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#91410
01/11/2003 2:13 PM
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Joined: Jun 2002
Posts: 161
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wwh ,
according to Biochemistry by L. Stryer, Fe (iron) while coordinated in heme and supported by hemoglobin (the protein) binds oxygen. "The iron atom in heme can form 6 bonds or coordinate links, which are not identical to valence . 4 of these are in the plane of the heme. The fifth bond is occupied by histidine (amino acid) F8, O2 is bound at the sixth bond"
i must add that (AFAIK) most proteins are colourless and prostetic groups, for example ions are responsible for their colour. see rav's post
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