Molecular oxygen is produced during __________.

• A. stomatal opening
• B. the Calvin cycle
• C. cyclic electron flow during the light reactions
• D. re-energization of electrons by PSI
• E. linear electron flow during the light reactions

Answer: (E)

Verified step by step guidance

1. Understand that molecular oxygen (O₂) is a byproduct of photosynthesis, specifically during the light-dependent reactions.
2. Recall that the light-dependent reactions occur in the thylakoid membranes of chloroplasts and involve the absorption of light by chlorophyll.
3. Recognize that water molecules (H₂O) are split during the process known as photolysis, which occurs in the light-dependent reactions.
4. Identify that the splitting of water molecules releases electrons, protons, and oxygen gas (O₂). This process is part of the linear electron flow.
5. Conclude that molecular oxygen is produced during the linear electron flow of the light reactions, not during stomatal opening, the Calvin cycle, cyclic electron flow, or re-energization of electrons by PSI.