The Calvin cycle, Calvin–Benson–Bassham (CBB) cycle, reductive pentose phosphate cycle or C3 cycle is a series of biochemical redox reactions that take place in the stromaof chloroplast in photosynthetic organisms.NADPH (Nicotinamide adenine dinucleotide phosphate) and ATP. The rate-limiting step in the Calvin cycle is the point where glycerate 3-phosphate is reduced. Unless a plant is heavily shaded, or the sun is rising or setting, light intensity is not usually the limiting factor.