The gas produced during respiration is carbon dioxide (CO2). During cellular respiration, cells break down glucose and oxygen to generate energy, a process producing carbon dioxide as a waste product. This CO2 is then transported back to the lungs, where it is expelled from the body during exhalation. In plants, respiration occurs alongside photosynthesis, which uses carbon dioxide and sunlight to produce glucose and oxygen. Maintaining a balance of CO2 in the body is crucial for regulating pH and ensuring efficient cellular function.