Number of NADPH + H+ molecules used during the conversion of CO2 into one molecule of glucose through C3 cycle, is :

The Calvin cycle, also known as the C3 cycle, is the process by which a photosynthetic organism makes glucose from carbon dioxide.

In the Calvin cycle, each CO2 molecule is attached to a five-carbon sugar named ribulose bisphosphate (RuBP) by an enzyme called RuBisCO, resulting in a six-carbon sugar that quickly splits into two molecules of 3-phosphoglycerate (a three-carbon compound).

Each 3-phosphoglycerate is then phosphorylated by ATP and reduced by NADPH + H+ to produce glyceraldehyde 3-phosphate (G3P), a carbohydrate molecule.

For one molecule of glucose (a six-carbon sugar), two molecules of G3P are required. Therefore, the Calvin cycle must turn six times and fix six molecules of CO2.

Each turn of the cycle consumes 2 NADPH + H+ molecules (for the reduction of 3-phosphoglycerate to G3P). Therefore, to produce one glucose molecule, the Calvin cycle uses 12 NADPH + H+ molecules (2 NADPH per cycle x 6 cycles).