Question

Dark reaction involves utilisation of CO₂ in producing C₆H₁₂O₆ (glucose). Why is this phase called dark reaction?

Answer 1

The term 'dark reaction' does not mean that it only occurs at night. This simply indicates that the reactions are not dependent on light. This phase is also known as the biosynthetic phase. The Calvin cycle is named after Melvin Calvin, who discovered the reaction. In this step, NADPH’s hydrogen is combined with CO₂ using ATP energy to form glucose (C₆H₁₂O₆). The synthesis process involves numerous steps and the use of intermediary molecules such as RuBP. This reaction can be summarised using the chemical equation below:

\[\ce{6RuBP + 6CO2 + 18ATP + 12NADPH + 12H+ -> 6RuBP + C6H12O6 + 18ADP + 18Pi + 12NADP + 6H2O}\]