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Old 13 April 2012, 05:51 PM
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Blow Your Top Hemoglobin and chlorophyll

Comment: I read that, from a molecular standpoint, the only difference
between chlorophyll and human blood is in the center atom. In human blood,
the center atom is iron, and in chlorophyll, it is magnesium. Is this
true?
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Old 13 April 2012, 05:53 PM
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Glasses

Hemoglobin:



Chlorophyll:

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Old 13 April 2012, 06:48 PM
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So what's the answer then?

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Old 13 April 2012, 06:55 PM
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I know next to nothing about chemistry, but even if that were true (that the only difference is the atom at the center) that would still be quite a substantial difference, no?
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Old 13 April 2012, 07:08 PM
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Quote:
Originally Posted by Alarm View Post
So what's the answer then?
They're similar but (aside from the center atom) not identical:

http://alliedhealthblog.com/2010/11/...nd-hemoglobin/
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Old 13 April 2012, 07:24 PM
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Nitpick: that's heme, not hemoglobin. Hemoglobin is a complex of the heme group and the much larger globin protein.

ETA: There's also the name for the general structure: a porphyrin ring.

ETA2: Even more biochemistry fun - both are derived from the same precursor, protoporphyrin IX, as shown in this pathway diagram.
Here's it's structure for comparison.


Isn't biochemistry fun!

Last edited by Jahungo; 13 April 2012 at 07:39 PM.
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Old 13 April 2012, 07:47 PM
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A Turtle Named Mack A Turtle Named Mack is offline
 
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Quote:
Originally Posted by Gin Rickey View Post
I know next to nothing about chemistry, but even if that were true (that the only difference is the atom at the center) that would still be quite a substantial difference, no?
Maybe, maybe not. In most organic molecules, the side groups from the main chains and rings are what makes the biggest difference. If there is an atom of something besides the usual culprits (C, O, H, N, S: I think those are the regulars), then it might just be a sort of placeholder. OTOH, the odd atom's electronegativity (attraction for charged particles) can make a subtle but crucial difference in the way it reacts. For instance since hemoglobin needs to be able to both hold onto and release O2 and CO2, you can imagine that the difference between an iron atom and some other metal might be critical. Of course, if animals had started using copper for some reason, then the structure of the hemoglobin-function molecule would probably have evolved differently to be efficient with a copper in it, rather than an iron. Then we could be Vulcans.
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Old 13 April 2012, 09:18 PM
Nick Theodorakis Nick Theodorakis is offline
 
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Quote:
Originally Posted by A Turtle Named Mack View Post
... Of course, if animals had started using copper for some reason, then the structure of the hemoglobin-function molecule would probably have evolved differently to be efficient with a copper in it, rather than an iron. Then we could be Vulcans.
Actually, the oxygen carrier used in many invertebrate animals is hemocyanin, which is a copper metalloprotein (although not a hemoprotein).

Nick
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Old 13 April 2012, 09:21 PM
jimmy101_again jimmy101_again is offline
 
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While hemoglobin binds both molecular oxygen and carbon dioxide the heme group (see Jahungo's post) just binds the molecular oxygen. The carbon dioxide binding site is not at the heme.

The proteins that hold the heme and chlorophyll are a fair bit different and contribute pretty significantly to the different activities.
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Old 13 April 2012, 09:35 PM
Nick Theodorakis Nick Theodorakis is offline
 
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Although carbon monoxide does bind to the heme, and in fact more strongly than oxygen does, which is why it's so dangerous.

Nick
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  #11  
Old 16 April 2012, 06:16 AM
Troberg Troberg is offline
 
 
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Well, they are not the same, even if that central atom is ignored, but they are clearly related. One can't help but wonder what would happen if one was to replace the central atom in chlorophyll and try to replace hemoglobin with the "hemophyll". Or, for that matter, doing the opposite and try to replace chlorophyll with "chloroglobin".

It sure would be some nice science.

Perhaps we'd turn green in the sun instead of getting a tan?
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