Lactate and the Oxygen Debt

Biology Unit 5

Lactate and the Oxygen Debt

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Biology Unit 5
Revision Notes
Topic 7: Run for your life
11. Explain the fate of lactate after a period of
anaerobic respiration in animals.
Lactate is oxidised back to pyruvate to enter the Krebs cycle to be respired, producing carbon
dioxide, water and ATP. Lactate removed from muscles and carried to the liver in the blood is
converted back to pyruvate and then glucose by gluconeogenesis. The glucose is then carried
around in the blood to replenish the glycogen stores in the muscles.
The current consensus is that there are seven factors affecting our post-exercise oxygen needs:
Oxidation of lactate to pyruvate to move into the Krebs cycle
Lactate removed from muscles and carried to the liver in the blood is converted back to
pyruvate and then into glucose by gluconeogenesis. The glucose is then carried around in the
blood to replenish the glycogen stores in the muscles
ATP and phosphocreatine levels in the muscle fibres need to be restored, which takes
oxygen from the Krebs cycle
Myoglobin in the muscles needs to be reoxygenated
All chemical reactions, including those of respiration, go faster ­ so more oxygen is needed.
This is the result of raised temperatures in the muscles and hormones such as adrenaline
which are released during exercise, both of which increase reaction rates
We need to breathe more deeply and rapidly during exercise ­ and so the muscles of the
ribs and diaphragm use more oxygen
The heart rate is elevated for a time after exercise so the heart muscle needs extra oxygen
supplies for the increased respiration required to support this.
Text Book: p. 133 - 134

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