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How do photosynthesis and cellular respiration cycle carbon and oxygen through living systems?

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A herd of African elephants stands at the edge of the Chobe River in Botswana, drinking water with a backdrop of dry hills and scattered green trees. — life A herd of African elephants (*Loxodonta africana*) drinking from the Chobe River, Botswana.

Photosynthesis and cellular respiration function as complementary processes that cycle carbon and oxygen through the biosphere.

The Carbon and Oxygen Cycle

Photosynthesis: Producers, such as plants and algae, capture sunlight to convert carbon dioxide and water into energy-rich carbohydrates. During this process, oxygen is released as a vital by-product into the atmosphere and water.123
Cellular Respiration: Organisms use oxygen to oxidize these organic compounds, releasing the stored chemical energy needed for life-sustaining activities. As a result of this breakdown, carbon dioxide and water are discarded as waste products and returned to the environment.145

This continuous exchange ensures that carbon is fixed into organic matter by producers and later released back into the atmosphere by consumers and decomposers, while oxygen is consumed and replenished in a balanced cycle. This relationship is fundamental to the maintenance of life on Earth, as it regulates the atmospheric levels of these essential elements.123