What is photosynthesis?
Photosynthesis is the process plants, algae and some bacteria use to turn sunlight, water and carbon dioxide into sugar for food, releasing oxygen as a by-product.
Photosynthesis takes place mainly in leaves, inside tiny structures called chloroplasts. They contain chlorophyll, a green pigment that absorbs red and blue light. The energy from the light is used to split water molecules and to combine carbon dioxide from the air into glucose, a simple sugar.
The overall reaction can be written as six molecules of carbon dioxide plus six molecules of water, with light energy, producing one molecule of glucose and six molecules of oxygen. Plants use the sugar for energy and to build stems, leaves, roots and fruit.
Why it matters to everyone
Almost all food chains on Earth start with photosynthesis, and it supplies the oxygen we breathe. Tiny ocean organisms called phytoplankton carry out about half of the planet's photosynthesis. The process also removes carbon dioxide from the air, which helps regulate the climate.
Did You Know?
The oxygen released in photosynthesis comes from the water molecules, not from the carbon dioxide, as scientists showed in the 1940s using special forms of oxygen.