Science
How does photosynthesis work?
Photosynthesis works in two stages: light-dependent reactions capture sunlight in the chloroplasts to make energy carriers, then the Calvin cycle uses that energy to turn carbon dioxide and water into glucose, releasing oxygen.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how photosynthesis works.
Step by step
- 1Chlorophyll in the chloroplasts absorbs sunlight (mainly red and blue light).
- 2Light reactions split water, release oxygen, and store energy in molecules called ATP and NADPH.
- 3The Calvin cycle uses that stored energy to build glucose from carbon dioxide.
- 4Overall: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.
Frequently asked questions
- What are the two stages of photosynthesis?
- The light-dependent reactions (capture sunlight, split water, release oxygen) and the Calvin cycle (build glucose from CO₂ using the captured energy).
- Where does photosynthesis happen?
- Mostly in the leaves, inside chloroplasts that contain the green pigment chlorophyll.
- Why does photosynthesis release oxygen?
- Oxygen is a by-product of splitting water molecules during the light-dependent reactions.