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Answer: Breathing is a mechanical process of exchanging gases between an organism and its surroundings.In humans, you use lungs, which absorb gases. When you breathe in air, you take in a mixture of gases:Oxygen: about 21%
Carbon dioxide: about 0.03%
Nitrogen: about 78%
Rare gases: about 0.97%
Water vapour: amount varies
You breathe out:Oxygen: about 16%
Carbon dioxide: about 4%
Nitrogen: about 78%
Rare gases: about 0.97%
Water vapour: lots
Some of the oxygen you breathe in goes into the blood stream to be used in respiration.
Carbon dioxide is a waste product of respiration and in the lungs it passes out of the blood and is breathed out.
Respiration is a chemical process when glucose or other sugars react with oxygen to produce energy. It produces carbon dioxide and water as waste products. The equation for respiration is:Glucose + Oxygen = Carbon dioxide + Water + EnergyC6H12O+ 6O2 = 6CO2 + H2O + Energy

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