Glucose is a simple sugar and a vital source of energy for living organisms, while carbon dioxide is a byproduct of metabolism and does not provide energy.
Specifically, when glucose is broken down in a process called cellular respiration, it releases energy stored in its chemical bonds. The complete oxidation of one molecule of glucose (C6H12O6) can yield about 36 to 38 ATP (adenosine triphosphate) molecules, which are the energy currency of cells. This equates to approximately 686 kilocalories (kcal) of energy.
In contrast, carbon dioxide (CO2) is formed during the metabolic processes when glucose is oxidized for energy. CO2 itself does not contain usable energy; instead, it is a waste product that is expelled by organisms.
Thus, to answer the question, glucose has a significant energy content utilized by the body, while carbon dioxide does not have any energy content in this context. The comparison is fundamentally about energy production versus waste output in the metabolic cycle.