Final answer:
The formula for lactic acid fermentation, common in muscle cells during intense activity and in some bacteria like those in yogurt, is Pyruvic acid + NADH → lactic acid + NAD+.
Step-by-step explanation:
The formula for lactic acid fermentation is:
Pyruvic acid + NADH → lactic acid + NAD+
In this biochemical process, pyruvic acid (which is produced during glycolysis) undergoes reduction, with the help of the enzyme lactate dehydrogenase, to form lactic acid. During this reaction, NADH is oxidized to NAD+, which is then available to once again participate in glycolysis. This fermentation method occurs in muscle cells under strenuous activity when oxygen is scarce and in certain bacteria, such as those that produce yogurt. The produced lactic acid from muscle cells is then transported to the liver via blood circulation for further metabolism.
Lactic acid fermentation allows for ATP production under anaerobic conditions and creates lactic acid as the end product, distinguishing it from other types of fermentation, such as alcoholic fermentation that produces ethanol and carbon dioxide.