* ATP (adenosine triphosphate): This is the energy currency of the cell, providing the energy required for the Calvin cycle to occur.
* NADPH (nicotinamide adenine dinucleotide phosphate): This is a reducing agent that carries high-energy electrons, which are used to reduce carbon dioxide (CO2) into glucose.
The light-dependent reactions capture light energy and use it to:
* Split water molecules (photolysis), releasing oxygen as a byproduct and generating electrons.
* Energize those electrons by moving them through an electron transport chain.
* Use the energy from the energized electrons to generate ATP and NADPH.
These ATP and NADPH molecules then move from the light-dependent reactions to the stroma of the chloroplast, where the Calvin cycle takes place. Here, they are used to drive the following steps:
1. Carbon fixation: CO2 is incorporated into an organic molecule, ribulose bisphosphate (RuBP), with the help of the enzyme rubisco.
2. Reduction: The carbon molecules are reduced using energy from ATP and electrons from NADPH. This results in the formation of glucose.
3. Regeneration: RuBP is regenerated to continue the cycle.
Therefore, the light-independent portion of photosynthesis is fueled by the ATP and NADPH produced in the light-dependent reactions. These molecules provide the energy and reducing power necessary to convert carbon dioxide into glucose.
