Light Independent Reaction

The light Independent Reaction NADPH and ATP from light-dependent reactions used to power glucose synthesis. Light not directly necessary for light-independent reactions if ATP & NADPH available. Light-independent reactions are called the Calvin Cycle.

Carbon fixation CO2 is covalently linked to a carbon skeleton (RuBP) CO2 enters plants from air, goes into stroma CO2 attaches to ribulose bisphosphate (RuBP), product of which is immediately split into two molecules of glycerate 3-phosphate Reaction is catalysized by an enzyme called rubisco.

Reduction 2. Carbohydrate is formed at the expense of ATP and NADPH the glycerate 3- phosphate is energized and reduced by ATP and NADPH from the light reactions to make triose phosphate (TP).

Triose phosphate siphoned off from this part of the Calvin cycle represents the carbohydrate product of photosynthesis. Triose phosphate is a three-carbon sugar-phosphate that can be used to make a range of carbohydrates by other pathways.

Regeneration 3. The CO2 acceptor RuBP reforms using the energy from ATP. The remaining triose phosphate is converted into more ribulose-1,5-bisphosphate (RuBP) so that the Calvin cycle can continue to go around again. Requires an ATP and more than one triose phosphates to give the total of five carbons found in RuBP.

Explain the light-independent reactions of photosynthesis (8 Marks)