A healthy adult receives glucose solution through a vein for the first 30 minutes of an investigation. The glucose supply is then stopped. No food or drink containing carbohydrate is given during the investigation.
The table shows the results.
| Time after start / min | Blood glucose concentration / mmol dm−3\mathrm{mmol\,dm^{-3}}mmoldm−3 | Relative insulin concentration | Relative glucagon concentration |
|---|---|---|---|
| 0 | 5.0 | 6 | 10 |
| 30 | 8.2 | 26 | 5 |
| 90 | 5.6 | 10 | 8 |
| 150 | 4.2 | 4 | 19 |
| 240 | 4.9 | 6 | 11 |
Explain why the relative insulin concentration at 90 minutes is lower than at 30 minutes but remains higher than at 0 minutes.
A student concludes that stopping the glucose supply is the only factor that determines the glucagon concentration after 30 minutes.
Explain why the results do not support this conclusion.
On another occasion, a drug prevents liver cells from responding to glucagon from 150 minutes onwards.
Suggest how the blood glucose concentration at 240 minutes would be affected by the drug.
Explain how the results show that the control of blood glucose concentration is an example of negative feedback.
94 exam-style questions on Edexcel GCSE Biology 7.4 Blood glucose and the urinary system, covering 7.4.1 Insulin and blood glucose control, 7.4.2 Glucagon and blood glucose regulation, 7.4.3 Type 1 and type 2 diabetes, 7.4.4 Structure of the urinary system, 7.4.5 Structure and function of the nephron, 7.4.6 ADH and water regulation, 7.4.7 Treatments for kidney failure, and 7.4.8 Production of urea in the liver. Each one has a worked solution and a mark scheme showing where the marks go.