Anaerobic respiration in muscles and fatigue, reading lactic acid and oxygen uptake graphs, the oxygen debt and the liver (Higher), trained and untrained athletes, and glycogen data for metabolism.
What you will learn
- Explain when and why muscles respire anaerobically and why they fatigue
- Read lactic acid graphs and calculate a rate of removal
- Calculate an oxygen debt from an oxygen uptake graph and explain how lactic acid is removed (Higher)
- Compare trained and untrained athletes from data
- Classify metabolic reactions and work with glycogen data
When oxygen runs short
During hard exercise the heart rate and breathing rate rise, but oxygen still cannot reach the muscles fast enough.
The muscles also respire anaerobically.
In muscle cells: glucose → lactic acid
The incomplete oxidation of glucose releases much less energy than aerobic respiration, and lactic acid builds up. During long periods of vigorous activity muscles become fatigued and stop contracting efficiently.
- Clothes peg squeezes: 72 in minute 1, 44 in minute 5
- Fall = 72 − 44 = 28
- 28 ÷ 72 × 100 = 38.9% decrease (3 s.f.)
The rest of this lesson and its 12 practice questions are locked.
In this lesson
- When oxygen runs short
- Reading a lactic acid graph
- The oxygen debt (Higher)
- Metabolism
- Try it: Read the peak
12 practice questions, marked as you go; about 30 minutes in all.
Key terms
Anaerobically, Incomplete oxidation, Lactic acid, Oxygen debt, Liver, Glucose, Metabolism
In this unit: Bioenergetics: photosynthesis and respiration
Photosynthesis and its rate, limiting factors and the pondweed practical, aerobic and anaerobic respiration, exercise and metabolism.