Here's why:

* NADPH (nicotinamide adenine dinucleotide phosphate) is a crucial electron carrier in the light-dependent reactions of photosynthesis.

* It receives high-energy electrons from the chlorophyll molecules in photosystems I and II.

* These electrons are then used to power the Calvin cycle, which converts carbon dioxide into sugar.

Other important molecules in photosynthesis:

* ATP (adenosine triphosphate) is also a vital energy carrier in photosynthesis.

* Rubisco is an enzyme that plays a key role in the Calvin cycle.

Let me know if you'd like more details about any of these!