Science
What is Photosynthesis?
Photosynthesis is the process plants, algae, and some bacteria use to turn sunlight, water, and carbon dioxide into glucose (food) and oxygen. It is the chemical reaction that powers almost all life on Earth and produces the oxygen we breathe.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains photosynthesis.
Key things to understand
- 1It happens mainly in the leaves, inside tiny structures called chloroplasts that contain the green pigment chlorophyll.
- 2Inputs: carbon dioxide (from the air) + water (from the roots) + light energy (from the Sun). Outputs: glucose (stored energy) + oxygen (released).
- 3The overall reaction: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.
- 4It has two stages: the light-dependent reactions (capture energy) and the Calvin cycle (build sugar).
Frequently asked questions
- Why is photosynthesis important?
- It produces the oxygen most living things need and forms the base of nearly every food chain by converting light energy into chemical energy.
- Do plants photosynthesize at night?
- No. Photosynthesis needs light, so it stops at night. Plants still respire (use oxygen) around the clock.
- What is chlorophyll?
- Chlorophyll is the green pigment in chloroplasts that absorbs sunlight — mostly red and blue light — to drive photosynthesis, which is why most plants look green.