Final answer:
In muscle cells, fermentation produces lactate and NAD+ through the process of lactic acid fermentation, which occurs under anaerobic conditions and allows glycolysis to continue generating ATP.
Step-by-step explanation:
In muscle cells, fermentation specifically refers to lactic acid fermentation. During this biochemical process, pyruvate produced from glycolysis is reduced to lactate, also known as lactic acid. This process regenerates NAD+ from NADH, which is essential for allowing glycolysis to continue so that the cells can continue making ATP. Unlike alcoholic fermentation, which produces ethanol and carbon dioxide, lactic acid fermentation does not produce these substances.
Essentially, in muscle cells under anaerobic conditions, such as during intense exercise when oxygen is scarce, lactic acid fermentation helps to produce the energy needed by converting pyruvate into lactic acid and simultaneously converting NADH back into NAD+. This is critical because it allows glycolysis to continue producing ATP. Therefore, the correct answer to the question is that fermentation in muscle cells produces lactate and NAD+.