The Calvin cycle occurs in the stroma of the chloroplasts in plant cells. The stroma is the fluid-filled space surrounding the thylakoid membranes inside the chloroplast. This is where carbon dioxide is fixed and converted into sugars using ATP and NADPH produced by the light-dependent reactions of photosynthesis
. Despite sometimes being called "dark reactions," the Calvin cycle does not occur in the dark but depends on the products of light reactions, so it takes place when light is available
. The cycle involves three main phases-carbon fixation, reduction, and regeneration-all happening within the chloroplast stroma
. In summary, the Calvin cycle takes place in the chloroplast stroma, the inner fluid space of chloroplasts outside the thylakoid membranes, where it synthesizes sugars from carbon dioxide using energy carriers generated by the light reactions of photosynthesis.
