Chloroplast· Photosynthesis, end to end

Kinetics after Farquhar, von Caemmerer & Berry (1980), simplified to a dynamic two-reservoir (ATP/NADPH) scheme.

Light600µmol·m⁻²·s⁻¹

CO₂420ppm

O₂21%

Temperature25°C

Live readouts

t = 0s

Net CO₂ assimilation0.0µmol·m⁻²·s⁻¹

O₂ evolution0.0µmol·m⁻²·s⁻¹

ATP synthesis0%

NADPH synthesis0%

Photorespiration0%

Sugar (G3P) output0%

Energy reservoirs

ATP pool0%

NADPH pool0%

Enzymes

How it works

The chloroplast is the solar power plant of a plant cell. Light striking the stacked thylakoid membranes (the grana) drives the light reactions: water is split — releasing O₂ — electrons are passed down a chain that pumps protons into the thylakoid lumen, and the returning proton flood spins ATP synthase to make ATP, while NADPH is made at the far end. Out in the surrounding fluid — the stroma — those two energy carriers power the Calvin cycle, where the enzyme RuBisCO fixes CO₂ into sugar. RuBisCO is imperfect: it also grabs O₂ in a wasteful side-reaction called photorespiration, which worsens when CO₂ is scarce, O₂ is high, or it gets hot. Move the sliders and watch the whole coupled system find a new balance.