What is Photosynthesis?
Photosynthesis is the process by which green plants, algae, and some bacteria use light to make their own food. They combine light energy with water and carbon dioxide to produce glucose (a type of sugar) and oxygen. This is the foundation of most life on Earth because it provides the oxygen we breathe and forms the base of most food chains.
Why plants need light
Light energy from the sun drives the chemical reactions in photosynthesis. Without light, plants cannot make glucose and would not have energy to grow.
Where it happens
The process mainly takes place in the chloroplasts of plant cells. Chloroplasts contain a green pigment called chlorophyll that captures light energy.
The two main stages
- Light-dependent reactions (in the thylakoid membranes):
- Light is absorbed by chlorophyll.
- Water molecules are split (photolysis) to release oxygen gas.
- Energy-rich molecules (ATP and NADPH) are produced.
- Calvin cycle / light-independent reactions (in the stroma):
- Uses ATP and NADPH to convert carbon dioxide into glucose (a sugar).
Overall equation (simplified)
Carbon dioxide + water + light energy → glucose (sugar) + oxygen
Why photosynthesis matters
- Produces the oxygen we breathe.
- Provides the base of the food chain for almost all organisms.
- Helps regulate Earth's atmosphere and climate.
Quick recap
Plants use light to turn water and carbon dioxide into glucose for energy and growth, releasing oxygen in the process. This happens mainly in chloroplasts through light-dependent reactions and the Calvin cycle.