Which of the following is an input required for the light-dependent reactions of photosynthesis?

• A. Glucose (\(C_6H_{12}O_6\))
• B. Water (\(H_2O\))
• C. Oxygen (\(O_2\))
• D. Carbon dioxide (\(CO_2\))

Answer: (B)

Verified step by step guidance

1. Understand the light-dependent reactions of photosynthesis: These reactions occur in the thylakoid membranes of chloroplasts and require light energy to produce ATP and NADPH, which are used in the light-independent reactions.
2. Identify the key inputs for the light-dependent reactions: The primary inputs are light energy, water (\(H_2O\)), and ADP + Pi (to form ATP). Water is split during photolysis to provide electrons, protons, and oxygen.
3. Eliminate incorrect options: Glucose (\(C_6H_{12}O_6\)) is a product of photosynthesis, not an input for the light-dependent reactions. Oxygen (\(O_2\)) is released as a byproduct during photolysis, not an input. Carbon dioxide (\(CO_2\)) is used in the Calvin cycle (light-independent reactions), not the light-dependent reactions.
4. Focus on water (\(H_2O\)): Water is essential for the light-dependent reactions because it provides electrons to replace those lost by chlorophyll in photosystem II during the process of photolysis.
5. Conclude that water (\(H_2O\)) is the correct input required for the light-dependent reactions of photosynthesis.