In which part of photosynthesis is oxygen produced?

• A. Calvin cycle
• B. Dark reaction
• C. Light-dependent reaction
• D. Light-independent reaction

Answer: (C)

Oxygen is produced during the light-dependent reactions of photosynthesis. This process occurs in the thylakoid membranes of chloroplasts, where light energy is captured and converted into chemical energy. Water molecules are split in a process called photolysis, releasing oxygen as a byproduct. The light-dependent reactions also generate ATP and NADPH, which are essential for the subsequent light-independent reactions, or Calvin cycle, where carbon fixation occurs.

The other options do not lead to the production of oxygen. The Calvin cycle and dark reactions involve the conversion of carbon dioxide into glucose using the energy produced in the light-dependent reactions but do not produce oxygen. The light-independent reactions occur in the absence of light and focus on synthesizing sugar rather than the generation of oxygen.