The Light-Independent Reaction

• The light-independent reaction is otherwise known as the Calvin Cycle.
• The Calvin Cycle requires the ATP and reduced NADP from the LDR to reduce glycerate 3-phosphate. It takes place in the stroma and it doesn't directly require sunlight.
• Firstly, CO2 diffuses into the leaf through the stomata and dissolves in water around the walls of the mesophyll cells. It then diffuses through all membranes in the chloroplast till it reaches the stroma.
• Once the CO2 has reached the stroma, it reacts with ribulose bisphosphate (RuBP), a 5 carbon compound. This reaction is catalysed by the rubisco enzyme.
• The symbol equation for the reaction between CO2 and ribulose bisphosphate is : CO2 + RuBP -> 2GP.
• After the CO2 and RuBP reaction, the reduced NADP (from the LDR) is used to reduce GP to triose phosphate (TP) using energy supplied by ATP. NADP is reformed, and is recycled in the LDR.
• The triose phosphate produced in the LIR has two roles. Firstly, some TP is converted into organic molecules (e.g. glucose/amino acids). However, most TP is used to regenerate RuBP using ATP from the LDR.