The essential function of converting pyruvic acid to lactic acid in an oxygen starved muscle is to
Correct answer: A. regenerate NAD so that glycolysis can continue
- A. regenerate NAD so that glycolysis can continue
- B. produce a large amount of ATP directly
- C. remove carbon dioxide from the cell
- D. activate the enzymes of the Krebs cycle
Explanation
Glycolysis needs a constant supply of oxidised NAD, and without oxygen the electron transport chain cannot regenerate it, so reducing pyruvate to lactate does that job instead. The step itself makes no ATP at all, but it keeps the two ATP per glucose of glycolysis flowing. This is why a sprinting muscle can work for a short time with no oxygen and accumulates lactate as it does so.
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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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