How is energy yield compared between aerobic and anaerobic respiration?

Aerobic respiration yields more energy than anaerobic respiration, with up to 38 ATP molecules compared to just 2 ATP.

Aerobic and anaerobic respiration are two types of cellular respiration processes that occur in living organisms to produce energy. The key difference between these two processes lies in the presence or absence of oxygen, which significantly impacts the amount of energy produced.

Aerobic respiration, as the name suggests, requires oxygen. It is a three-step process that includes glycolysis, the Krebs cycle, and the electron transport chain. Glycolysis, which occurs in the cytoplasm, breaks down one molecule of glucose into two molecules of pyruvate, yielding a net gain of 2 ATP. The pyruvate then enters the mitochondria, where it undergoes the Krebs cycle and the electron transport chain, producing a further 36 ATP. Therefore, the total energy yield from one glucose molecule in aerobic respiration is up to 38 ATP.

On the other hand, anaerobic respiration occurs in the absence of oxygen. It also begins with glycolysis, but the pyruvate produced is then converted into lactic acid (in animals) or ethanol (in plants and yeast) instead of entering the mitochondria. This process, known as fermentation, does not produce any additional ATP beyond the 2 ATP generated in glycolysis. Therefore, the total energy yield from one glucose molecule in anaerobic respiration is just 2 ATP.

In summary, aerobic respiration is far more efficient in terms of energy production than anaerobic respiration. However, anaerobic respiration allows organisms to survive and produce energy in environments where oxygen is scarce or absent. It's important to note that while the ATP yield is significantly higher in aerobic respiration, both processes are essential for life on Earth.