A student completes two rides on an exercise bicycle. Each ride lasts 3 minutes. She pedals at the same rate during both rides, but the resistance is different.
During the low-resistance ride, enough oxygen reaches her muscle cells for aerobic respiration. During the high-resistance ride, her muscle cells respire anaerobically as well as aerobically.
The table shows her results.
| Time breathing rate is measured | Breathing rate for the low-resistance ride / breaths per minute | Breathing rate for the high-resistance ride / breaths per minute |
|---|---|---|
| Before the ride | 14 | 14 |
| Straight after the ride | 24 | 34 |
| 2 minutes after stopping | 16 | 25 |
Calculate the percentage of the increase in breathing rate caused by the high-resistance ride that remains 2 minutes after stopping.
Give your answer to the nearest whole number.
Compare the student's breathing-rate response to the two resistance levels and explain why her breathing rate takes longer to return towards its resting value after the high-resistance ride.
The student completes each ride only once.
Suggest one change to the investigation that would improve the evidence for the effect of resistance on breathing-rate recovery.
113 exam-style questions on OCR GCSE Biology 1.3 Respiration, covering 1.3.1 Cellular respiration supplies ATP, 1.3.2 Aerobic and anaerobic respiration, 1.3.3 Sugars and carbohydrates, 1.3.4 Amino acids and proteins, and 1.3.5 Fatty acids and lipids. Each one has a worked solution and a mark scheme showing where the marks go.