In muscle cells, fermentation produces _____.

• A. glucose
• B. ethanol
• C. oxygen
• D. lactic acid

Answer: (D)

Verified step by step guidance

1. Understand the context: Fermentation is an anaerobic process (occurs without oxygen) that allows cells to produce energy when oxygen is not available. In muscle cells, this process is crucial during intense exercise when oxygen supply is limited.
2. Recall the types of fermentation: There are two main types of fermentation—alcoholic fermentation and lactic acid fermentation. Alcoholic fermentation produces ethanol and carbon dioxide, while lactic acid fermentation produces lactic acid.
3. Identify the type of fermentation in muscle cells: Muscle cells undergo lactic acid fermentation, not alcoholic fermentation, because they do not produce ethanol.
4. Connect the process to the product: During lactic acid fermentation, glucose is broken down into pyruvate through glycolysis. Pyruvate is then converted into lactic acid to regenerate NAD⁺, which is essential for glycolysis to continue.
5. Conclude the answer: The product of fermentation in muscle cells is lactic acid, which allows energy production to continue under anaerobic conditions.