What is the difference between lactic acid and alcoholic fermentation?

Lactic acid fermentation produces lactic acid, while alcoholic fermentation produces ethanol and carbon dioxide.

Lactic acid fermentation and alcoholic fermentation are two types of anaerobic respiration that occur in cells when oxygen is not present. Both processes begin with glycolysis, which breaks down glucose into pyruvate. For more details on glycolysis, you can refer to our notes on glycolysis and ATP production. However, the fate of pyruvate differs in each type of fermentation.

In lactic acid fermentation, pyruvate is converted into lactic acid by the enzyme lactate dehydrogenase. This process occurs in muscle cells during intense exercise when oxygen is not available to produce energy through aerobic respiration. To understand the stages of aerobic respiration, see our notes on stages and locations of aerobic respiration. Lactic acid fermentation also occurs in bacteria, such as those used to make yoghurt and sauerkraut.

In alcoholic fermentation, pyruvate is converted into ethanol and carbon dioxide by the enzyme alcohol dehydrogenase. This process occurs in yeast and some bacteria, such as those used to make bread and beer. For an in-depth look at anaerobic processes, check our notes on anaerobic respiration in cells. The carbon dioxide produced during alcoholic fermentation is responsible for the bubbles in bread dough and beer. More about this can be found in our notes on anaerobic respiration.

A-Level Biology Tutor Summary: Lactic acid fermentation produces lactic acid and occurs in muscle cells and some bacteria, while alcoholic fermentation produces ethanol and carbon dioxide and occurs in yeast and some bacteria. Both processes start with glycolysis but differ in the final products, helping cells produce energy when oxygen is not available.