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calvin cycle (dark rxn)

Discussion in 'DAT Discussions' started by joonkimdds, Jan 7, 2009.

  1. joonkimdds

    joonkimdds Senior Member
    7+ Year Member

    Jun 30, 2005
    Likes Received:
    DAT destroyer says 6 cycle is required to make 1 glucose.
    I am wondering why it takes 6 cycle instead of 2 cycle.

    1 cycle = 3 CO2, 9ATP, 6NADPH added to Rubisco and 3RuBP.

    It becomes 6 of 3PGA ==> 6 of G3P and only 1 of them is used to make glucose.

    Since G3P is 3carbon, and glucose is 6 carbon, we need to repeat this cycle one more time to make 2 of G3P = 2 of 3 carbon = 6 carbon = glucose.

    so I think only 2 cycles are required to make 1 glucose instead of 6 cycle.

    Another question I have is, what do the concentration of H and Mg2+ stored in chlorophyll have something to do about this cycle?
  2. Svart Aske

    Svart Aske is stabbing his eyes out
    10+ Year Member

    Jun 7, 2008
    Likes Received:
    Each cycle only starts with 1 CO2 and 1 RuBP (not 3), so it takes 6 cycles to produce a glucose.

    I don't have my textbook with me, but I think Mg is just a component of the chlorophyll pigment, while the H+ concentration difference across the lumen and thylakoid membrane of the chloroplast creates an electrochemical gradient that makes chemiosmosis, and hence ATP production, possible.
    #2 Svart Aske, Jan 7, 2009
    Last edited: Jan 7, 2009

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