Lactic acid that accumulates in a vigorously exercising muscle is mainly
Correct answer: D. carried in the blood to the liver and reconverted to glucose
- A. excreted unchanged in the urine
- B. converted back to glucose within the muscle fibre itself
- C. completely oxidised in the muscle within seconds
- D. carried in the blood to the liver and reconverted to glucose
Explanation
Muscle lacks the enzymes to run gluconeogenesis, so lactate diffuses into the blood and the liver rebuilds it into glucose in the Cori cycle, using ATP from oxygen taken in after exercise. That extra oxygen consumption is the oxygen debt, which is why heavy breathing continues after a sprint has finished. Only a very small fraction of lactate is lost in urine or sweat.
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About Cellular Respiration
Cellular respiration releases energy from glucose through glycolysis, the link reaction, the Krebs cycle and the electron transport chain, producing ATP. The pathway differs in oxygen availability: aerobic respiration uses oxygen and yields more ATP, while anaerobic respiration produces much less ATP and forms lactic acid in muscles or ethanol and carbon dioxide in yeast.
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