NADP⁺ (Nicotinamide Adenine Dinucleotide Phosphate) is primarily a hydrogen (electron) acceptor — it accepts two electrons and one proton (H⁺) to become NADPH during the light-dependent reactions of photosynthesis (in Photosystem I). NADPH then donates these electrons/hydrogen in the Calvin cycle (light-independent reactions) to reduce $\text{CO}_2$ into sugars. It is not an ion carrier or enzyme activator in the primary sense.