Final answer:
NADP+ is the molecule that is reduced by high-energy electrons to form NADPH during the light-dependent reactions of photosynthesis, which is then used in the Calvin cycle to help convert carbon dioxide into organic molecules.
Step-by-step explanation:
During photosynthesis, high-energy electrons are used to reduce certain molecules. The molecule NADP+ is reduced to NADPH during the light-dependent reactions.
This is a critical step in the process as NADPH provides the reducing power necessary for the subsequent light-independent reactions known as the Calvin cycle.
Here, NADPH is used alongside ATP for the conversion of 3-phosphoglycerate (3-PGA) into glyceraldehyde-3-phosphate (G3P) in a reduction reaction.
This step is crucial because it involves the gain of electrons by 3-PGA, which is part of the process of turning inorganic carbon dioxide into organic compounds like glucose.
It is important to note that carbon dioxide (CO2) is not reduced during the light-dependent reactions but during the light-independent reactions of the Calvin cycle, where it combines with ribulose bisphosphate (RuBP) in a series of reactions facilitated by the enzyme Rubisco and eventually turns into glucose.
Therefore, the correct answer to the question is NADP+, which is reduced to NADPH, and carbon dioxide is later incorporated into organic molecules in the Calvin cycle.