Which of the following statements about the light-dependent reactions of photosynthesis is correct?

• A. They use carbon dioxide and produce glucose.
• B. They use water and produce oxygen as a byproduct.
• C. They do not require light to proceed.
• D. They occur in the stroma of the chloroplast.

Answer: (B)

Verified step by step guidance

1. Step 1: Begin by understanding the light-dependent reactions of photosynthesis. These reactions occur in the thylakoid membranes of the chloroplast and require light energy to proceed.
2. Step 2: Recognize the key inputs and outputs of the light-dependent reactions. The primary inputs are water (H₂O) and light energy, while the outputs include oxygen (O₂) as a byproduct, ATP, and NADPH.
3. Step 3: Clarify the role of water in the process. Water molecules are split during photolysis, a process driven by light energy, to release electrons, protons, and oxygen gas (O₂). This oxygen is released as a byproduct.
4. Step 4: Address the incorrect statements in the problem. Light-dependent reactions do not use carbon dioxide or produce glucose directly; these processes occur in the light-independent reactions (Calvin cycle). Additionally, light-dependent reactions require light and do not occur in the stroma but in the thylakoid membranes.
5. Step 5: Conclude that the correct statement is: 'They use water and produce oxygen as a byproduct,' as this accurately describes the light-dependent reactions of photosynthesis.