Which statement about lactic acid in muscle fibers is true?

• A. Lactic acid is stored in muscle fibers for long-term energy use.
• B. Lactic acid is the primary source of energy for muscle contraction.
• C. Lactic acid is produced during anaerobic respiration when oxygen levels are low.
• D. Lactic acid accumulation in muscles leads to increased pH levels.

Answer: (C)

Verified step by step guidance

1. Understand the context of lactic acid production: Lactic acid is produced in muscle fibers during anaerobic respiration, which occurs when oxygen levels are insufficient for aerobic respiration.
2. Recognize the role of lactic acid: It is not stored for long-term energy use nor is it the primary source of energy for muscle contraction. Instead, it is a byproduct of anaerobic metabolism.
3. Clarify the effects of lactic acid accumulation: Lactic acid accumulation in muscles actually leads to decreased pH levels, causing muscle fatigue and soreness, not increased pH levels.
4. Identify the correct statement: The correct statement is that lactic acid is produced during anaerobic respiration when oxygen levels are low.
5. Review the physiological implications: During intense exercise, muscles may rely on anaerobic respiration, leading to lactic acid buildup, which is eventually cleared from the muscles and converted back to pyruvate or glucose in the liver.