Transporting substances to cells
The vast number of chemical reactions that take place in your cells need a continual supply of energy. They get this energy from the food that you eat, but just taking in the fuel is not enough. Oxygen is needed to react with the fuel, which is mainly glucose, in order to release the energy. This important process is called respiration. (As the process uses oxygen it is more correctly called aerobic respiration.) Your cells are respiring as you sit and read this. The process can be summarised in an equation:
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