The answer is (1) releases energy. In the cells of the human body, oxygen molecules are used directly in a process of cellular respiration during which energy is released. In cellular respiration, glucose and oxygen yield carbon dioxide and water and energy is released in the form of adenosine triphosphate: C₆H₁₂O₆ (glucose) + O₂ (oxygen) → H₂O (water) + CO₂ (carbon dioxide) + ATP (adenosine triphosphate).