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Name: Jack
Status: other
Grade: other
Location: Outside U.S.
Country: Australia
Date: Spring 2013


Question:
Hi, Ive been researching about Chlorophyll and found that iron is essential for chloropyhll production and that an excess of Iron can disrupt the formation of Chlorophyll. As chlorophyll is bonded to a central mg ion, is it possible for Fe2+, to replace the magnesium ion? and if it is possible does it mean that it forms a plant version of heme - similar to heme found in hemoglobin?



Replies:
Hi Jack,

Thanks for the question. The size of the Mg2+ ion is much smaller than the size of the Fe2+ ion, so it is unlikely that Fe2+ (the ferrous ion) will be able to fit into the center of the chlorophyll molecule. Remember, the purpose of chlorophyll is to trap light energy; chlorophyll is not directly involved in bonding or reacting to oxygen. Thus, it is unlikely that this simple substitution will generate a plant version of heme. However, a plant version of heme could be produced, but many more changes in the amino acids and porphyrin ring would be necessary.

I hope this helps. Please let me know if you have more questions. Thanks Jeff


Thank you Phil for your reply, your answer was very easy to understand and was a big help. I have been continuing research on Iron's role in Chlorophyll and in particular an over excess of Iron.

According to research another reason why excess iron can cause damage to cells is because Fe is required in and as co-factors in reactions that create δ-aminolevulinic acid. In excess Fe, the δ-aminolevulinic acid is created at faster rates, as more Iron containing enzymes are present. After a few more chemical reactions Protochlorophyllide is synthesised, and due to the high amounts of δ-aminolevulinic acid, Protochlorophyllide, the precursor to chlorophyll-a also becomes accumulated in high concentrations. Protochlorophyllide acts as a photosensitiser and can produce free radicals which can bond to chemicals inside the plant and destroy cells? I was wondering if this information is correct, or if I am just making it up? Also if it was correct would the free radicals produced be enough to severely damage the plant and have a heavy impact on its growth?

In a scientific report I found it is suggested that Protochlorophyllide was converted by the protein LPOR in a light dependant reaction. The LPOR hold both NADPH and Protochlorophyllide and when a photon hits this, a hydrogen from LPOR and NADPH, reduces Protochlorophyllide. I thought NADPH was used as a part of the calvin cycle and photosynthesis? Or is Chlorophyll made in the photosynthesis process?

I also found that Fe and some other transition metals can react with Hydrogen peroxide to produce free radicals? If this is so could this process occur in a plant? If free radicals indirectly produced by excess iron aren't the cause of the symptoms of Fe toxicity, do you know any reasons as to why?

I hope these new questions aren't too much to ask. Thank you very much for your time, Jack



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