This page describes glycolysis as the anaerobic breakdown of glucose in the cytosol, yielding two pyruvic acid molecules and ATP. Pyruvic acid then undergoes fermentation in yeasts (producing ethanol ...This page describes glycolysis as the anaerobic breakdown of glucose in the cytosol, yielding two pyruvic acid molecules and ATP. Pyruvic acid then undergoes fermentation in yeasts (producing ethanol and CO2) or lactic acid in red blood cells and muscles. Both fermentation routes are energy-inefficient. In contrast, pyruvic acid is fully oxidized in mitochondria during cellular respiration, capturing approximately 40% of glucose's energy as ATP.