1. Comparison of light reactions and oxidative phosphorylation:

    Feature

    Contrast (Oxidative)

    Contrast (Photosynthesis)

    Compare (Both)

    Organelle

    Mitochondrion

    Chloroplast

    Endosymbionts

    Compartments

    Matrix, IMS

    Stroma, lumen/IMS

     

    Route

    NADH → O2

    H2O → NADPH

    Similar but backwards

    Overall reaction

    O2 makes HO2O

    H2O makes O2

    Ditto

    Electron carriers

    Cytochrome-c

    Plastocyanin, ferredoxin

    Quinones (Q-cycle), flavins, FeS

    Energy source

    NADH (needed once)

    Light (needed twice)

    Carried by electrons

    Chemiosmotics

    Mostly (∆Em) electrogenic

    Mostly (∆pH) proton concentration

    ATP synthase using proton gradient

    Energy budget

    c. 2.5 ATP per NADH

    c. 1.5 ATP per H2O

     
  2. Calvin cycle summary.
  3. The following features of photosynthesis evolved in:
    • ATPases in Archaea for nutrient cotransport.
    • Action spectrum of photosynthesis due to being shaded by bacteriorhodopsin.
    • Photosystem I in sulfur bacteria, using photons to channel electron from H2S to ferredoxin.
    • Calvin cycle in sulfur bacteria as a way of running Krebs/PPP backwards to generate sugar from CO2.
    • Photosystem II (and cyt-b/f) in purple non-sulfur bacteria as a way of generating ATP by cyclic electron transport and the Q-cycle.
    • Water splitting evolved in cyanobacteria, because PSI and PSII in series were strong enough to reduce water. This removed the need for H2S.