If the respiratory system fails, the person would be unable to obtain the necessary oxygen needed by the cells to carry out aerobic respiration. The oxygen combines with glucose in the cells' mitochondria and A.T.P. is formed when the chemical energy in the bonds of glucose is released. A.T.P. is energy currency the cells use to carry out metabolic functions. If the respiratory system fails, excess carbon dioxide and water, which are waste products of cellular respiration would be unable to be excreted by the lungs properly. This would affect homeostasis in the body. Diseases of the respiratory system that could affect its performance include asthma, emphysema, lung cancer for example.