Name the two major stages of photosynthesis and their locations.

Name the two major stages of photosynthesis and their locations.

• A. Light-dependent reactions in thylakoid membranes; Calvin cycle in the stroma
• B. Krebs cycle in mitochondria and electron transport chain on inner mitochondrial membrane
• C. Glycolysis in cytoplasm; fermentation in cytoplasm
• D. Dark reactions in nucleus; light reactions in cytoplasm

Answer: (A)

The two main stages of photosynthesis are the light-dependent reactions and the Calvin cycle. The light-dependent reactions occur in the thylakoid membranes of the chloroplasts, where light energy drives electron transport, splits water to release oxygen, and produces ATP and NADPH. The Calvin cycle happens in the chloroplast stroma, using that ATP and NADPH to fix carbon dioxide into sugars (like glyceraldehyde-3-phosphate). This placement—light reactions in the thylakoids and the Calvin cycle in the stroma—accurately reflects how the process is organized in the chloroplast. Other options mix in processes from cellular respiration (like Krebs cycle and electron transport chain in mitochondria) or place reactions in incorrect locations (dark reactions in the nucleus, light reactions in the cytoplasm).

The two main stages of photosynthesis are the light-dependent reactions and the Calvin cycle. The light-dependent reactions occur in the thylakoid membranes of the chloroplasts, where light energy drives electron transport, splits water to release oxygen, and produces ATP and NADPH. The Calvin cycle happens in the chloroplast stroma, using that ATP and NADPH to fix carbon dioxide into sugars (like glyceraldehyde-3-phosphate). This placement—light reactions in the thylakoids and the Calvin cycle in the stroma—accurately reflects how the process is organized in the chloroplast. Other options mix in processes from cellular respiration (like Krebs cycle and electron transport chain in mitochondria) or place reactions in incorrect locations (dark reactions in the nucleus, light reactions in the cytoplasm).