Figure 8.18 The Calvin cycle has three stages. In stage 1, the enzyme RuBisCO incorporates carbon dioxide into
an organic molecule, 3-PGA. In stage 2, the organic molecule is reduced using electrons supplied by NADPH. In
stage 3, RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue. Only one carbon
dioxide molecule is incorporated at a time, so the cycle must be completed three times to produce a single threecarbon
GA3P molecule, and six times to produce a six-carbon glucose molecule.