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Biology Paper 1 · B4 · Lesson 4.10

Higher Tier: oxygen debt and recovery

Follow lactic acid from working muscles to the liver.

Key ideas1 of 2

Define oxygen debt

Higher Tier only. Oxygen debt is the extra oxygen needed after exercise to deal with accumulated lactic acid and remove it from cells. Breathing and heart rate remain elevated during recovery.

After exercise, oxygen uptake falls towards resting uptake. The shaded area above resting uptake represents extra oxygen used during recovery; schematic.

Link recovery to the earlier period of anaerobic respiration.

Next: Higher Tier exam practice →
Topic resources and sources

Daily 5 · Core exam practice · Higher Tier questions · A4 revision sheet

Lessons 4.1–4.8 cover the core. Lessons 4.9–4.10 are Higher Tier only. Daily 5 practises core facts.

AQA Combined Science Trilogy specification · 4.4.2.2 · Higher Tier only. Original notes, questions and diagrams. Experimental numbers are illustrative.

Photographs: pondweed by Frank Vincentz; dough by ElinorD, both CC BY-SA 3.0. Polytunnel by Bob Nichols / USDA, public domain. Images displayed without cropping or other alterations.