What is cellular respiration?

Cellular respiration is the process by which cells convert glucose and oxygen into energy in the form of ATP (adenosine triphosphate), along with producing carbon dioxide and water as byproducts. This process is vital for all aerobic organisms as it provides the necessary energy to fuel cellular activities and sustain life. During cellular respiration, glucose, a simple sugar, undergoes a series of metabolic reactions, including glycolysis, the Krebs cycle, and oxidative phosphorylation, ultimately resulting in the efficient capture of energy stored in chemical bonds.

While breakdown of fats can also release energy, that describes a specific aspect of cellular metabolism known as fatty acid oxidation, and does not encompass the full definition of cellular respiration. The conversion of sunlight into chemical energy pertains to photosynthesis, a process carried out by plants and certain bacteria, which is fundamentally different from how cells derive energy. The cycling of carbon through ecosystems refers to biogeochemical cycles, which include processes beyond respiration, such as photosynthesis and decomposition, and does not specifically address how cells derive their energy. Hence, the first option accurately encapsulates the central concept of cellular respiration.