During a clinical trial, a medicine was suspected of affecting how the liver processes excess amino acids.
The table shows the mean blood concentrations before and after a group of people took the medicine for seven days.
| Time of measurement | Ammonia concentration in mmol per dm³ | Urea concentration in mmol per dm³ |
|---|---|---|
| Before taking the medicine | 0.04 | 5.0 |
| After seven days | 0.16 | 3.8 |
Calculate the percentage decrease in the mean urea concentration after seven days.
The clinical trial was stopped because the medicine might be dangerous.
Explain how the changes in the table could have been caused by the medicine and why they might be dangerous.
85 exam-style questions on AQA GCSE Biology 5.3 Hormonal coordination in humans, covering 5.3.1 Human endocrine system, 5.3.2 Control of blood glucose concentration, 5.3.3 Maintaining water and nitrogen balance in the body, 5.3.4 Hormones in human reproduction, 5.3.5 Contraception, 5.3.6 The use of hormones to treat infertility (HT only), and 5.3.7 Negative feedback (HT only). Each one has a worked solution and a mark scheme showing where the marks go.