Scientists investigate a chemical messenger, H, produced by a gland in a mammal. They stimulate the gland to release H and take blood samples.
| Blood sample | Concentration of H in the blood in pg cm⁻³ |
|---|---|
| entering the gland | 2 |
| leaving the gland | 26 |
The scientists also measure the concentration of H in the blood entering three organs. They calculate the change in the activity of each organ after the gland is stimulated.
| Organ | Concentration of H in the blood entering the organ in pg cm⁻³ | Change in activity of the organ in % |
|---|---|---|
| P | 22 | 0 |
| Q | 21 | +40 |
| R | 20 | 0 |
Explain what the results show about how H is released from the gland and which organ responds specifically to H.
The scientists separate a blood sample containing H into blood plasma and red blood cells. The red blood cells are washed to remove any plasma. Equal volumes of the plasma and the washed red blood cells are added separately to identical living samples of cells from organ Q.
Explain which sample of cells is expected to show the greater response to H.
89 exam-style questions on Edexcel GCSE Biology 7.1 Hormones and coordination, covering 7.1.1 Endocrine glands and hormone transport, 7.1.2 Adrenalin and fight or flight, and 7.1.3 Thyroxine and negative feedback. Each one has a worked solution and a mark scheme showing where the marks go.