The Calvin cycle is the principle mechanism by which plants convert carbon dioxide captured from the atmosphere into sugar, starch and other carbohydrates. The Calvin cycle occurs in three steps. (1). Carboxylation phase- here, a carbon dioxide molecule is added to a sugar called ribulose which gets converted to a 3-carbon molecule called 3 PGA (3-phosphoglycerate). (2.) Reduction phase- here, 3PGA is converted into a 3- carbon sugar called G3P( glyceraldehyde -3-phospate). (3)Regeneration phase- in this step, G3P is used to make fructose diphosphate which is then used to make glucose, sucrose, starch and other carbohydrates which we consume in our food.