Our bodies need energy to move and do work. Where do we get our energy from? The energy is obtained from the food that we and all other organisms eat. If you think back to the work you did on fuel and energy in previous grades in Energy and Change, you will remember that fuels, such as wood, coal, and oil, contain chemical potential energy. When this fuel is burned in the presence of oxygen, the chemical potential energy is transferred into light and heat energy. In the same way, the glucose from the food that you eat is combined with oxygen in a series of chemical reactions to release the energy. The glucose is broken down and the energy is released. This energy is then used to drive all the other processes in your body. This process is called respiration. We can define respiration in all living organisms as the process by which energy is released from glucose in a series of chemical reactions. Respiration takes place in all organisms, even plants. However, plants do not need to eat any food as they make their own food during photosynthesis.

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