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Every cell in your body needs energy. Cells get their energy from
food by a chemical reaction called respiration.
Digestion breaks down carbohydrates and complex sugars into a simple
sugar called glucose. This is the fuel that cells use in respiration,
and it is carried around your body in your bloodstream. The glucose
reacts with oxygen (from your lungs) to make carbon dioxide and water.
The reaction releases energy. Your blood carries the waste carbon
dioxide and water to your lungs so that it can be breathed out.
