Photosynthesis, step by step
How a leaf turns sunlight, water and air into food and the oxygen you are breathing right now — narrated step by step.
Sunlight reaches the leaf
Every meal you have ever eaten started with sunlight landing on a leaf. A plant is a machine for catching light and turning it into food, and it runs silently, all day, everywhere.
Chlorophyll absorbs the light
Inside the leaf are tiny green packets called chloroplasts, filled with a pigment called chlorophyll. Chlorophyll soaks up red and blue light and reflects green, which is exactly why leaves look green to you.
Roots draw up water
Meanwhile the roots are drinking. Fine root hairs pull water out of the soil, and a large tree can lift hundreds of litres of it in a single summer day.
Leaf pores take in carbon dioxide
On the underside of the leaf are thousands of microscopic mouths called stomata. They open to let carbon dioxide in from the air, which is where every carbon atom in the plant comes from.
Water travels up the stem
Water climbs the stem through narrow tubes called xylem, pulled upward by evaporation at the top. There is no pump anywhere in a plant, just a very long unbroken thread of water.
Light splits the water molecules
Now the clever part. The absorbed light energy is strong enough to split water molecules apart into hydrogen and oxygen. This is the only natural process on Earth that routinely takes water apart at everyday temperatures.
Oxygen is released into the air
The oxygen is left over, so the plant simply breathes it out. Roughly half of the oxygen in every breath you take came from plants, and the other half from algae drifting in the ocean.
Energy is stored as ATP
The energy freed from the light is packed into two chemical batteries called ATP and NADPH. They cannot be stored for long, so the plant spends them almost immediately.
The Calvin cycle builds sugar
In the Calvin cycle the plant grabs carbon dioxide from the air and uses those batteries to bolt the carbon atoms together. It takes six carbon dioxide molecules to build one sugar.
Glucose feeds the plant
The result is glucose, a simple sugar that is both food and building material. The plant burns some of it for energy and rearranges the rest into stems, leaves and roots.
Extra sugar is stored as starch
Whatever is left over gets locked away as starch, a compact long term store. That starch is the potato, the grain of rice and the bread on your table.
The plant grows
So a plant is quietly assembling itself out of air, water and light. Every leaf you walk past is doing chemistry that no factory on Earth can match for efficiency or scale.
Watch it explain itself
Every step above is narrated aloud. Play it, or open it in the editor and make it yours — no account needed.