Final answer:
When oxygen is insufficient, the cell may perform anaerobic respiration, which results in the production of lactic acid instead of water as a byproduct of cellular respiration.
Step-by-step explanation:
Alternative Products Formed in Cellular Respiration
At the end of cellular respiration, instead of water, an alternative product that may be formed is lactic acid. This occurs during anaerobic respiration, when oxygen is scarce or absent, and the pyruvate from glycolysis is converted into lactic acid instead of entering the citric acid cycle. In the presence of oxygen, the typical end products of cellular respiration are carbon dioxide and water, and energy is captured in molecules of ATP. However, when oxygen is not present, such as during intense exercise, cells resort to anaerobic respiration to continue producing ATP, although in much smaller quantities. The overall process of cellular respiration involves breaking down glucose in the presence of oxygen to release energy, which is then used to convert ADP into ATP.