The Calvin cycle, a metabolic pathway found in the stroma of the chloroplast in which carbon enters in the form of CO2 and leaves in the form of sugar.report this answer.Updated on Thursday, February 02 2012 at 10:06AM EST.he Calvin cycle, a metabolic pathway found in the stroma of the chloroplast in which carbon enters in the form of CO2 and leaves in the form of sugar. report this answer. Updated on Thursday, February 02 2012 at 10:06AM EST.