Explain all three parts of oxygen debt removal
Connect continued circulation, breathing and the liver.
Section B12.1 · Respiration
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall cell processes, enzymes and the distinction between gas exchange and breathing.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Where is lactic acid transported in the specified recovery account?
What you will learn
- Transport lactic acid to the liver
- Supply oxygen for removal
Explain all three parts of oxygen debt removal
| Feature | Meaning |
|---|---|
| Transport | Fast heart rate: muscle → blood → liver |
| Oxygen supply | Continued deeper and faster breathing |
| Chemical removal | Aerobic respiration of lactic acid in liver |
| Scope | Limited Cambridge exam model |
Transport lactic acid to the liver
After vigorous exercise, the Cambridge removal model includes a continued fast heart rate. This supports transport of lactic acid in the blood from muscles to the liver. Name the material, carrier, starting site and destination. Saying only the heart removes the debt misses the transport route and treats pumping as the chemical removal reaction.
Continued deeper and faster breathing supplies oxygen for aerobic respiration of lactic acid. Both greater depth and greater rate are required in this part of the syllabus account. Air movement, gas exchange and blood oxygen transport connect that supply with the tissues; lactic acid is not described as being blown out of the mouth.
Supply oxygen for removal
The stated chemical removal in this limited exam model is aerobic respiration of lactic acid in the liver. Combine the three links: circulation carries lactic acid from muscle to liver, continued ventilation provides oxygen, and liver aerobic respiration removes lactic acid. The liver is therefore the named removal site, while heart and lungs support transport and supply.
Do not replace this syllabus answer with yeast fermentation or claim that the liver produces ethanol after exercise. The model is intentionally limited and is not a complete description of every real recovery pathway or all uses of extra recovery oxygen. A written answer should supply the three required links clearly while avoiding universal physiological claims beyond the model.
Sources for this lesson
Pause and explain
Which combined account is complete?
Worked example
Complete: muscles → blood → ___; deeper and faster breathing supplies ___ for the stated liver process.
Show the worked solution
- The lactic-acid destination is the liver.
- The supplied reactant is oxygen.
Answer Liver; oxygen, for aerobic respiration of lactic acid in the Cambridge model.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Explain the role of continued fast heart rate after vigorous exercise in this model.
Give me a hint
Name material, carrier and destination.
Compare my reasoning
- The heart maintains faster circulation.
- Lactic acid is carried in blood from muscles to liver.
Continued fast heart rate transports lactic acid in the blood from muscles to the liver.
Look for these in your work
- Name lactic acid and blood
- Give muscle-to-liver direction
Explain the breathing and liver roles together.
Give me a hint
Include both breathing depth and rate.
Compare my reasoning
- Deeper and faster breathing supplies oxygen.
- The liver carries out aerobic respiration of lactic acid in the model.
Continued deeper and faster breathing supplies oxygen for aerobic respiration of lactic acid in the liver.
Look for these in your work
- Include deeper and faster
- Name the liver process
Improve: recovery happens because the heart breaks lactic acid down and the lungs breathe it out.
Give me a hint
Separate pumping, oxygen supply and chemical removal.
Compare my reasoning
- The heart supports blood transport to liver.
- Breathing supplies oxygen; liver aerobic respiration is the stated removal.
Fast circulation carries lactic acid from muscles to liver; deeper and faster breathing supplies oxygen; aerobic respiration of lactic acid in the liver removes it in the Cambridge model.
Look for these in your work
- Correct both organ roles
- State all three links
Common mistakes
- Saying lactic acid is exhaled.
- Omitting either breathing depth or rate.
What can you explain now?
Which combined account is complete?
Compare with the explanation
Fast heart rate transports lactic acid to liver; deeper and faster breathing supplies oxygen; liver aerobic respiration removes it
All three required links are present.
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Make it stick
Explain all three required recovery links in one connected answer.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.