The primary product of anaerobic respiration is typically lactic acid or ethanol, depending on the organism. In the absence of oxygen, certain cells, such as muscle cells or yeast, convert glucose into energy through anaerobic pathways. In humans, this process results in lactic acid, which can accumulate during intense exercise, leading to muscle fatigue. Yeast, on the other hand, ferments glucose to produce alcohol and carbon dioxide, a process utilized in brewing and baking. Understanding anaerobic respiration is critical in fields such as physiology and microbiology.