IGCSE Biology glossary
Oxygen debt
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Definition
The amount of extra oxygen needed after vigorous exercise to break down the lactic acid that accumulated during anaerobic respiration. This is why breathing rate and heart rate remain elevated after exercise stops.
What to include in an exam answer
Oxygen debt explains heavy breathing after exercise. The lactic acid must be broken down: it is transported to the liver, where oxygen is used to convert it back to glucose or to oxidise it completely.
Example in context
Explain why a sprinter continues to breathe heavily after a race (3 marks): During the sprint, anaerobic respiration produced lactic acid. After the race, extra oxygen is needed to break down the lactic acid in the liver. The fast breathing supplies this extra oxygen to repay the oxygen debt.
Related syllabus topic
Respiration