The Light-Dependent Reactions of Photosynthesis

How can light energy be used to make food? When a person turns on a lamp, electrical energy becomes light energy. Like all other forms of kinetic energy, light can travel, change form, and be harnessed to do work. In the case of photosynthesis, light energy is converted into chemical energy, which photoautotrophs use to build basic carbohydrate molecules (Figure). However, autotrophs only use a few specific wavelengths of sunlight.

A photo shows the silhouette of a grassy plant against the sun at sunset.
Photoautotrophs can capture visible light energy in specific wavelengths from the sun, converting it into the chemical energy used to build food molecules. (credit: Gerry Atwell)
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