Photosynthesis: inputs, products and the role of chlorophyll
A quick science revision note explaining how plants use light energy to make sugars.
In photosynthesis, plants use light energy to convert carbon dioxide and water into sugars, releasing oxygen as a by-product. Chlorophyll absorbs light and helps capture the energy used in the process.
The simplified equation
A common simplified equation is: carbon dioxide + water + light energy → glucose + oxygen. The real process includes multiple chemical steps, but the equation is useful for school-level revision.
Chlorophyll is a pigment found in chloroplasts. It absorbs some wavelengths of light more strongly than others, helping drive the light-dependent reactions.
Common mistakes
Plants do not get most of their dry mass by absorbing soil. Carbon in the sugars comes primarily from carbon dioxide in the air, while water also supplies atoms used in the reactions.
Photosynthesis and cellular respiration are related but not identical processes. Photosynthesis stores energy in chemical compounds; respiration releases usable energy from them.
Editorial note
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Frequently asked questions
Which gas is released as a by-product of photosynthesis?
Oxygen.