The process cells use to convert glucose into energy in the absence of oxygen is called anaerobic respiration. This process involves the partial breakdown of glucose yielding energy, typically resulting in byproducts such as lactic acid in animals or ethanol and carbon dioxide in yeast. Anaerobic respiration is less efficient than aerobic respiration; however, it enables organisms to survive in low-oxygen environments. It plays a significant role in various biological processes and industries, such as fermentation and muscle metabolism during intense exercise.