Interactive Explainer
How does photosynthesis work?
Photosynthesis is the process plants use to convert light energy into stored chemical energy. In broad strokes, plants capture sunlight, use it to power reactions inside chloroplasts, and build sugars from carbon dioxide and water while releasing oxygen.
Plants use light to power the making of sugars from carbon dioxide and water. Oxygen is released along the way.
Light matters, but water supply, carbon dioxide, and temperature can all become the limiting factor that slows the whole system.
Photosynthesis feeds most food webs directly or indirectly and helps shape the oxygen content of the atmosphere.
Try It Yourself
Photosynthesis Lab
Brighten the light, enrich the carbon dioxide, dry the leaf out, or push temperature away from the sweet spot to see which factor starts throttling sugar production.
What changes the fastest
What is driving the result
The Big Idea
What is actually happening?
An interactive explainer about how plants capture light, use water and carbon dioxide to make sugar, and release oxygen as part of the process.
Pigments absorb light
Chlorophyll and other pigments absorb certain wavelengths of light and start the energy-transfer reactions inside the chloroplast.
Water is split and energy carriers are charged
Light-driven reactions help split water and load up short-term energy carriers the plant will use in later steps.
Carbon dioxide is fixed into organic molecules
Using that captured energy, the plant builds carbon-containing molecules that can eventually become sugars.
Sugars feed growth and storage
The plant can use the resulting sugars right away for living processes or store and redirect them into starch, cellulose, oils, and other materials.
Good Follow-Up Questions
The details are where this gets interesting
The short answer helps, but the edge cases and comparisons are what make the topic memorable.
Oxygen is a byproduct, not the final goal
From the plant’s perspective, the real goal is to store energy in useful molecules. Oxygen is released as part of the chemistry.
More sunlight is not always enough
If a leaf is short on water or carbon dioxide, or if temperature is too stressful, extra light cannot fully rescue the overall rate.
Leaves must balance gain against water loss
To bring in carbon dioxide, stomata open. But open stomata also let water escape, so drought can force the plant into a tradeoff.
Compare Scenes
Why one leaf is highly productive while another stalls
Photosynthesis is controlled by whichever major input is currently in shortest effective supply.
Fast Answers
Questions people usually ask next
Good science pages should answer the obvious follow-ups without making the reader hunt for them.