This illustration shows a circular cycle with three stages. Three molecules of carbon dioxide enter the cycle. In the first stage, the enzyme RuBisCO incorporates the carbon dioxide into an organic molecule. Six ATP molecules are converted into six ADP molecules. In the second stage, the organic molecule is reduced. Six NADPH molecules are converted into six NADP+ ions and one hydrogen ion. Sugar is produced. In stage three, RuBP is regenerated, and three ATP molecules are converted into three ADP molecules. RuBP then starts the cycle again. In the Calvin cycle, energy storage molecules from the light-dependent reactions are used to capture (fix) carbon dioxide molecules and build sugars.