hill reaction

Discussion in 'Plants: Science and Cultivation' started by ntdna, Apr 4, 2010.

  1. ntdna

    ntdna Member

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    i study plant biochemistry and in exercise there is a question not clear for me
    what is the relation between the dioxygen concentration in a chloroplaste solution and light and electron receptors (wich is fe3+)in this exercise.
     
  2. bjo

    bjo Active Member 10 Years

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    Hi,

    the Hill reaction was the first demonstration that oxygen is produced in photosynthesis from water. Also that oxygen can be produced in photosynthesis in the absence of carbon dioxide. It demonstrated that there are two separate processes in photosynthesis; oxygen production and carbon dioxide fixation.

    Production of oxygen from water is an oxidation. If something is being oxidised, something else must be reduced...you need an "electron acceptor". In Hill´s original experiment he used iron oxalate as the electron acceptor. The iron in this is present as the Fe+++ (ferric) ion, and in the Hill reaction, it accepts an electron (is reduced) to the ferrous Fe++ ion.

    Overall:
    functional chloroplasts in the presence of light catalyse the following reaction:

    2H2O + 4Fe+++ ----> O2 + 4H + 4Fe++

    Fe+++ is the electron acceptor in Hill´s original experiment, but other electron acceptors are more commonly used nowadays to demonstrate the reaction, and Fe+++ is not the natural acceptor in photosynthesis.
    The acceptor which functions naturally in the chloroplast is the molecule NADP+ which is reduced to NADPH.

    Hope that helps,
    Good Luck,
    Brian
     
  3. ntdna

    ntdna Member

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    thank you so much , you cant' imagine how much your answer helped me.
     

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