Photosynthesis Interactive Diagram

A clickable chloroplast cross-section. Tap the thylakoid to step through the light reactions, or the stroma to walk the Calvin cycle. Inputs and outputs are tagged at every step.

Click a labeled region to dive in.
Thylakoid · light reactions
The membrane discs stacked into grana. Sunlight splits water here, releasing O2 and building ATP + NADPH.
Step through →
Stroma · Calvin cycle
The fluid around the thylakoids. CO2 is fixed into sugar here, powered by the ATP + NADPH made next door.
Step through →

Inputs
    Outputs

      Inputs
        Outputs
          6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
          The classic textbook formula. It hides two coupled chemistries: the light reactions in the thylakoid membrane and the Calvin cycle in the stroma.
          Thylakoid membrane

          Light reactions

          Inputs
          • Light (photons)
          • H2O
          • NADP+, ADP + Pi
          Outputs
          • O2 (released to air)
          • NADPH
          • ATP
          Stroma

          Calvin cycle

          Inputs
          • CO2
          • NADPH
          • ATP
          Outputs
          • G3P (sugar precursor)
          • NADP+
          • ADP + Pi

          Per molecule of glucose

          stoichiometry

          Building one glucose takes 6 turns of the Calvin cycle, which means the light reactions must supply 18 ATP and 12 NADPH — and to make those, 12 H2O are split, releasing 6 O2. NADPH and ATP get recycled back to NADP+ and ADP, so the two halves of photosynthesis run as a continuous loop.