A scientist measured the concentrations of substances in blood entering and leaving two organs of a healthy person. The person had more amino acids than were needed for building proteins.
| Organ | Substance measured | Concentration entering the organ in mmol dm⁻³ | Concentration leaving the organ in mmol dm⁻³ |
|---|---|---|---|
| Liver | Total amino acids | 3.2 | 2.0 |
| Liver | Urea | 4.6 | 5.8 |
| Kidneys | Urea | 5.8 | 4.4 |
Calculate the percentage decrease in the concentration of amino acids as the blood passed through the liver.
Explain why the liver removes surplus amino acids from the blood and how this is linked to the changes in urea concentration across the two organs.
92 exam-style questions on AQA GCSE Biology 4.2 Respiration, covering 4.2.1 Aerobic and anaerobic respiration, 4.2.2 Response to exercise, and 4.2.3 Metabolism. Each one has a worked solution and a mark scheme showing where the marks go.