Final answer:
The requirement of oxygen differentiates aerobic from anaerobic metabolism, with aerobic processes using oxygen for ATP production in the mitochondria and anaerobic processes producing ATP in the cytosol without oxygen. Option 2 is correct.
Step-by-step explanation:
The fundamental difference that differentiates aerobic from anaerobic cellular metabolism is the requirement of oxygen.
Aerobic metabolism requires oxygen to produce ATP and takes place in the mitochondria, utilizing not only glucose but also proteins and fats as fuel sources. In contrast, anaerobic metabolism occurs in the absence of oxygen, primarily in the cytosol, and relies solely on glucose as a fuel source, resulting in the production of lactic acid and a small amount of ATP.
During intense, rapid exercises like sprinting, anaerobic metabolism predominates due to the immediate need for ATP when oxygen is scarce. Conversely, during prolonged activities such as marathon running, aerobic metabolism is the primary source of ATP production, as there is more time for the body to supply oxygen to the working muscles.