Answer:
Regeneration of RuBP
Explanation:
The Calvin cycle (C3), which is also referred to as the light independent reaction occurs after the light stage of photosynthetis. It occurs mainly in three stages viz: Carbon fixation and reduction stage has been mentioned in the question
The third stage is the regeneration stage.
After the synthesis of 6molecules of G-3-P which requires NADPH and ATP as sources of hydrogen and energy respectively, one of the G-3-P molecules is exported out of the cycle in order to contribute to the formation of other compounds (glucose molecule). The remaining 5molecules of Glyceraldehyde-3-phosphate is then used in a series of chemical reactions to regenerate the CO2 acceptor, RUBP, which will then continue CO2 assimilation for the Calvin cycle to continue. The NADP+ and ADP molecules produced during the reduction of PGA to 3GP will return to the light stage to continue the process as well.
