Animals use the respiratory system to breathe in oxygen and other gases and expel gases like CO2, right? O2 in, CO2 out.
<span>By rebonding with another phosphate molecule through oxidative phosphorylation, it becomes recharged and the ADP to ATP process can be restarted. This allows for more cellular energy to be produced, and more metabolic actions to be undertaken. This is the major aspect of cell respiration.</span>
Out of the photosynthesis (plants).