Where Does the Oxygen That is Liberated in Photosynthesis Come From?


Photosynthesis is a process by which plants convert carbon dioxide into organic compounds. Sunlight plays a critical role, while oxygen is released as a byproduct. Photosynthesis makes plants very important to humans, because humans need oxygen to breathe and release carbon dioxide when exhaling. Without plants, the atmosphere's oxygen supply would quickly be diminished.

Sunlight and Photosynthesis

  • The sun's rays are the first step in the process of photosynthesis. Sunlight hits the plant and parts of the plant's cells called chloroplasts absorb the light's energy. When water is introduced into the equation through rain or watering, the light energy is combined with the water. Then carbon dioxide interacts with it as well, causing a chemical reaction that creates simple sugars. The byproduct of this chemical process causes oxygen to be released.

Where Does the Oxygen Come From?

  • Oxygen is created almost as an afterthought in the photosynthesis process. The chemical process that results from combining light energy, water, and carbon dioxide creates simple sugars, but the oxygen that is introduced into the equation by water is not really required. Thus, the oxygen is released back into the atmosphere as a waste byproduct of the process. Ultimately, the oxygen comes from water, which contains oxygen as an ingredient in its composition.

Human and Plant Interdependence

  • Oxygen is a critical element in the air that humans breathe and is absolutely necessary to sustain life. Breathing releases carbon dioxide as a waste product much as photosynthesis releases oxygen. Plants and humans are therefore dependent on one another.


  • Photo Credit Plant image by Platinum Pictures from Fotolia.com
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