An Illustration of alcoholic fermentation shows Pyruvic acid produced by glycolysis is converted into alcohol and carbon dioxide. Lactic acid fermentation converts the pyruvic acid to lactic acid. The stages shown here are:

1. Glycolysis: In cytoplasm, 2 molecules of nicotinamide adenine dinucleotide in oxidized form molecules react with glucose to give pyruvic acid and 2 molecules of nicotinamide adenine dinucleotide in reduced form. In this, 2 molecules of Adenosine diphosphate are converted to Adenosine triphosphate.
2. Alcoholic fermentation: 2 molecules of nicotinamide adenine dinucleotide in reduced form acts on pyruvic acid to give 2 molecules each of carbon dioxide, ethyl alcohol and nicotinamide adenine dinucleotide in oxidized form.
3. Lactic acid fermentation: 2 molecules of nicotinamide adenine dinucleotide in reduced form acts on pyruvic acid to give 2 molecules of lactic acid and nicotinamide adenine dinucleotide in oxidized form.