During cellular respiration, it converts glucose into the energy the animal needs. Oxygen is taken in while carbon dioxide is released as a waste product. read more
The by products (besides energy and heat) are water and carbon dioxide. The CO2 may be used by plants for "photosynthesis" (the opposite of cellular respiration) and convert the CO2 (plus the water that they already possess or have obtained) to glucose and ultimately starch or cellulose. read more