Question

Which Calvin cycle steps are similar to those of the pentose phosphate pathway? Please list all the reactions that are common ( reactants, enzymes, and products ) between the pentose phosphate pathway and the Calvin cycle.

Answer 1

In pentose phosphate pathway a metabolic pathway that generates NADPH and five-carbon sugars such as ribose 5-phosphate from glucose 6-phosphate; also refered to as hexose monophosphate shunt and the phosphogluconate pathway / it includes oxidative reactions which produce NADPH and ribose 5-phosphates as well as nonoxidative reactions which together convert five-carbon sugar phosphates to gluconeogenic precursors of glucose 6-phosphate.

Glucose + 2 NADP⁺ + H₂O ----> ribose 5-phosphate + 2 NADPH + 2 H ⁺ + CO₂

the Calvin cycle uses NADPH to reduce carbon dioxide to generate hexoses, whereas the pentose phosphate pathway breaks down glucose into carbon dioxide to generate NADPH.

On the other hand calvin cycle ( dark reactions .i.e. light independent of photosynthesis in green plants)

6 CO₂ + 18 ATP + 12 NADPH + 12 H₂O -----> C₆H₁₂O₆ + 18 ADP + 18 Pi + 12 NADP⁺ + 6 H⁺