Photosynthesis Explained Simply (for Students)
Photosynthesis is how plants, algae, and some bacteria make their own food using light. It is also the reason there is oxygen in the air to breathe. Here is the simple version, then the detail you need for class.
The simple version
Plants take in carbon dioxide from the air and water from the soil. Using energy from sunlight, captured by the green pigment chlorophyll, they combine these into glucose (a sugar they use for food) and release oxygen as a by-product.
The word equation
Carbon dioxide + water → (light energy + chlorophyll) → glucose + oxygen.
In chemical symbols: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Two stages
Photosynthesis happens in two linked stages inside the chloroplasts of plant cells.
- •Light-dependent reactions: sunlight splits water, releasing oxygen and storing energy in molecules called ATP and NADPH.
- •The Calvin cycle (light-independent): that stored energy is used to build glucose from carbon dioxide.
Why it matters
Photosynthesis is the base of almost every food chain — it captures the sun's energy in a form other living things can eat. It also produces the oxygen that most life depends on.
Frequently asked questions
What are the reactants and products of photosynthesis?
Reactants: carbon dioxide and water (plus light energy). Products: glucose and oxygen.
Where does photosynthesis take place?
In the chloroplasts of plant cells, which contain the green pigment chlorophyll that absorbs light.
What is the difference between photosynthesis and respiration?
Photosynthesis builds glucose and releases oxygen using light; respiration breaks glucose down to release energy, using oxygen and producing carbon dioxide.