Is ATP our cell's "food"?

Just think of ATP as a packet of energy that is needed for movement i.e. muscle contraction and relaxation, the substances that cells secrete etc. It is sometimes called the universal energy molecule because nearly all organisms need this ENERGY molecule to carry out life (cellular) processes. ATP is not food. Food is what you eat. You don't eat ATP, nor do other cells 'eat' ATP, they just use it as an ENERGY source. ATP is created when we eat food, though. So organic molecules such as glucose in our food are needed in respiration in order to join ADP and inorganic phosphate. ADP + PI = ATP in respiration. Respiration is the process of releasing energy from the food we eat. If you brush up on the stages of respiration then you will understand what ATP is a bit better, seeing as it is the product of aerobic respiration. =]