Light-independent reactions of photosynthesis

The
sketch shows a cross-section of a chloroplast with the light-independent reactions
cycling in the stroma.
The steps shown are a summary of six cycles of the Calvin–Benson reactions.
Black balls signify carbon atoms. Appendix V details the reaction steps.
1 Six CO2 diffuse into a photosynthetic cell, and then into a chloroplast. Rubisco
attaches each to a RuBP molecule. The resulting intermediates split, so twelve
molecules of PGA form.
2 Each PGA molecule gets a phosphate group from ATP, plus hydrogen and
electrons from NADPH. Twelve PGAL form.
3 Two PGAL combine to form one glucose molecule.
4 The remaining ten PGAL receive phosphate groups from ATP. The transfer
primes them for endergonic reactions that regenerate the 6 RuBP.