Final answer:
Lactic acid is the fermentation product produced in an anaerobic muscle cell. It is produced through lactic acid fermentation, which occurs when muscle cells do not receive enough oxygen during intense activity. During this process, pyruvate is reduced using NADH, producing lactate (lactic acid) and regenerating NAD+.
Step-by-step explanation:
Lactic acid is the fermentation product produced in an anaerobic muscle cell. When muscle cells are deprived of oxygen during intense activity, they undergo lactic acid fermentation to produce ATP. This process involves the reduction of pyruvate using electrons carried by NADH, resulting in the production of lactate (lactic acid) and the regeneration of NAD+.