The process that leads to the breakdown of glucose without oxygen is called anaerobic respiration. This process allows cells to produce energy under oxygen-limited conditions, using enzymes to convert glucose into energy-rich molecules like ATP. In animals, the primary product is lactic acid, while in yeast and some bacteria, it results in alcohol and carbon dioxide. Although anaerobic respiration yields less energy compared to aerobic processes, it plays a critical role in environments where oxygen is scarce, supporting cellular functions in various organisms.