Samples X and Y each contain the same number of living nerve cells of the same type. The samples are kept under identical conditions, with glucose and oxygen available.
During each four-minute period, one sample transmits repeated nerve impulses while the other sample rests.
A scientist uses the rate of oxygen uptake as a measure of the rate of aerobic respiration.
| Period | Activity of sample X | Oxygen uptake by sample X in nmol per minute | Activity of sample Y | Oxygen uptake by sample Y in nmol per minute |
|---|---|---|---|---|
| 1 | repeated nerve impulses | 7.8 | rest | 3.1 |
| 2 | rest | 3.0 | repeated nerve impulses | 7.7 |
| 3 | repeated nerve impulses | 8.0 | rest | 3.2 |
| 4 | rest | 3.1 | repeated nerve impulses | 7.9 |
Explain the pattern in the results, including why the rate of oxygen uptake does not fall to zero during periods of rest.
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.