photosynthesis U.2 L.10

  • light absorbed by chlorophyll or pigment molecules associate with proteins in clusters (photosystems)

  • antenna complex : web of chlorophyll molecules, transfer energy to reaction centre

  • reaction centre : accepts electrons from chlorophyll

    • electrons transfer to pheophytin prior to leaving photosynthesis

  • non cyclic electron flow :

    • “ATP machine” uses energy to pump H+ ions across membrane, which drives ATP and NADPH production

    • Z-scheme

  • cyclical electron flow :

    • generates H+ gradient needed to make ATP

    • does not create NADPH

    • more ATP than NADPH needed in calvin cycle

  • photosynthesis is light independent reactions (calvin cycle - C3 plants)

  • calvin cycle steps :

    1. carbon fixation - CO2 added to 5-C molecule, unstable 6-C molecule, splits into 2 3-C molecules, catalyzed by RuBisCO

    2. reduction reactions - phosphorylation of the 3-C molecules, NADPH reduces phosphorylated molecule, 6 3-C molecules remain and one leaves the cycle

    3. BuBP regeneration - ATP needed to rearrange remaining molecules to regenerate original 5-C molecule