Which of the following are the main reactants required for the light reactions of photosynthesis?

• A. Carbon dioxide (CO\(_2\)) and ATP
• B. NADH and pyruvate
• C. Water (H\(_2\)O), light energy, and NADP\(^+\)
• D. Glucose (C\(_6\)H\(_{12}\)O\(_6\)) and oxygen (O\(_2\))

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the context of the problem. The light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts and are the first stage of photosynthesis. These reactions convert light energy into chemical energy in the form of ATP and NADPH.
2. Step 2: Identify the key reactants involved in the light reactions. The light reactions require water (H\(_2\)O) as a source of electrons, light energy to drive the process, and NADP\(^+\) as an electron acceptor to form NADPH.
3. Step 3: Eliminate incorrect options. Carbon dioxide (CO\(_2\)) is used in the Calvin cycle, not the light reactions. NADH and pyruvate are involved in cellular respiration, not photosynthesis. Glucose (C\(_6\)H\(_{12}\)O\(_6\)) and oxygen (O\(_2\)) are products of photosynthesis, not reactants in the light reactions.
4. Step 4: Focus on the correct answer. Water (H\(_2\)O) provides electrons through photolysis, light energy powers the excitation of electrons, and NADP\(^+\) is reduced to NADPH during the light reactions.
5. Step 5: Summarize the process. The main reactants for the light reactions are water (H\(_2\)O), light energy, and NADP\(^+\), which work together to produce ATP, NADPH, and oxygen (O\(_2\)) as a byproduct.