Which of the following molecules is the primary product of Photosystem I during the light reactions of photosynthesis?

• A. Glucose
• B. NADPH
• C. ATP
• D. O\(_2\)

Answer: (B)

Verified step by step guidance

1. Step 1: Begin by understanding the role of Photosystem I in the light reactions of photosynthesis. Photosystem I is primarily involved in the production of high-energy molecules that are used in the Calvin cycle.
2. Step 2: Recall that Photosystem I uses light energy to excite electrons, which are then transferred through a series of proteins in the electron transport chain.
3. Step 3: Recognize that the primary product of Photosystem I is NADPH, a molecule that acts as an electron carrier and provides reducing power for the Calvin cycle. This is distinct from ATP, which is produced by ATP synthase, and O\(_2\), which is a byproduct of Photosystem II.
4. Step 4: Eliminate incorrect options such as glucose, which is synthesized later in the Calvin cycle, and O\(_2\), which is generated by Photosystem II during the splitting of water molecules.
5. Step 5: Conclude that the correct answer is NADPH, as it is the molecule directly produced by Photosystem I during the light reactions of photosynthesis.