* CO2 (Carbon dioxide): This is the primary source of carbon for the cycle.
* ATP (Adenosine triphosphate): This molecule provides the energy needed for the reactions.
* NADPH (Nicotinamide adenine dinucleotide phosphate): This molecule carries reducing power, providing the electrons needed for the reactions.
The Calvin cycle also uses RuBP (ribulose bisphosphate), a five-carbon sugar, as an initial reactant. However, RuBP is regenerated within the cycle, so it's not technically a reactant that is supplied from outside.
It's important to remember that the Calvin cycle doesn't require darkness to occur. It can happen in the presence of light as long as there is ATP and NADPH available, which are produced during the light-dependent reactions of photosynthesis.
