Question

How many ATP and NADPH molecules will be required to make one molecule of glucose through the Calvin pathway?

Answer 1

Part 1: The Calvin cycle
In the C3 pathway or Calvin cycle, the carboxylation of a five-carbon compound called RuBP results in the formation of a stable product called 3-Phosphoglycerate. The reduction of 3-Phosphoglycerate is an energy consuming process. Thus in this step one molecule of ATP and NADPH is used for one 3-PGA molecule. Further when RuBP is regenerated, another molecule of ATP is used.

Part 2: Energy molecules used
Six turns of the calvin cycle results in the formation of one molecule of glucose. For one turn: ATP used = 3 molecules NADPH used = 2 molecules Thus for six cycles : ATP used = 3*6 = 18 molecules NADPH used = 2*6 = 12 molecules Therefore total ATP and NADPH required to produce one molecule of glucose is 18 and 12 respectively.