Oxygen Debt
Biology: AQA GCSE Higher, topic 4.2.6
Anaerobic Respiration
If muscles are not supplied with enough oxygen during long periods of activity (like exercise), then muscle cells may start to respire anaerobically. This can lead to oxygen debt:
Lactic acid
- Lactic acid is a by-product of anaerobic respiration.
- Lactic acid is toxic. When it builds up in muscles, this can cause muscular pain and fatigue.
- Lactic acid also stops muscles contracting efficiently.
Oxygen debt
- Oxygen debt refers to the extra oxygen that is needed after exercise to oxidise lactic acid and get it out of cells.
Repaying the debt
- Blood transports the lactic acid to the liver, where it reacts with oxygen to produce carbon dioxide and water.
- Heavy breathing after exercise helps to repay the oxygen debt by taking more oxygen into the lungs.
Test yourself on Oxygen Debt
Why do muscle cells begin to respire anaerobically during long periods of intense exercise?
Why can a build-up of lactic acid cause muscular pain and fatigue during exercise?
A runner's muscles stop contracting efficiently near the end of a long race. What is the most likely cause of this?
Why does an athlete continue to breathe heavily for some time after finishing hard exercise?
Why does the liver react lactic acid with oxygen after exercise?