Primary End Products of Anaerobic Respiration: Lactic Acid and Ethanol

The two predominant end products of anaerobic respiration are lactic acid and ethanol:

1. Lactic Acid: Produced in human skeletal muscle cells during high‑intensity exercise when oxygen supply is insufficient for aerobic metabolism. Accumulation contributes to muscle fatigue and soreness; it is cleared once oxygen availability improves.
2. Ethanol (Alcohol): Generated by yeast and certain bacteria during alcoholic fermentation. Ethanol is a key component of alcoholic beverages and a biofuel; its production is a cornerstone of industrial fermentation.

Both pathways regenerate NAD⁺ from NADH, allowing glycolysis to continue producing ATP in the absence of oxygen. The specific end product depends on the organism and tissue type.