Aerobic respiration produces a total of 6 molecules of water, while anaerobic respiration typically produces none.
In aerobic respiration, glucose is completely oxidized in the presence of oxygen. The overall equation can be summarized as:
Glucose + Oxygen → Carbon Dioxide + Water + Energy
During this process, each molecule of glucose reacts with 6 molecules of oxygen to produce 6 molecules of water and 6 molecules of carbon dioxide, in addition to ATP, the energy currency of cells.
On the other hand, anaerobic respiration occurs in the absence of oxygen, and the process varies between different organisms. For instance, in yeast, the fermentation of glucose primarily produces ethanol and carbon dioxide instead of water:
Glucose → Ethanol + Carbon Dioxide + Energy
In muscle cells during strenuous exercise, glucose can be converted into lactic acid, again not producing water:
Glucose → Lactic Acid + Energy
Therefore, while aerobic respiration generates water as a byproduct, anaerobic processes do not typically produce water at all.