A model fish gill contains water representing blood inside a membrane that is permeable to dissolved oxygen. Fresh water flows past the outside of the membrane, keeping the oxygen concentration outside constant. No oxygen is used inside the model.
| time in minutes | oxygen concentration outside the membrane (mg dm⁻³) | oxygen concentration inside the membrane (mg dm⁻³) |
|---|---|---|
| 0 | 8.0 | 2.0 |
| 10 | 8.0 | 6.0 |
| 20 | 8.0 | 8.0 |
Explain how the net movement of oxygen across the membrane changes during the 20 minutes.
At 20 minutes, the water on both sides of the membrane is warmed from 15 °C to 25 °C. The oxygen concentrations are kept at the values shown for 20 minutes.
Explain the effect of this temperature increase on the movement of oxygen particles across the membrane.
102 exam-style questions on Edexcel GCSE Biology 8.1 Exchange surfaces and diffusion, covering 8.1.1 Introduction to exchange and transport, 8.1.2 Alveoli adapted for gas exchange, 8.1.3 Factors affecting rate of diffusion, and 8.1.4 Rate of diffusion using Fick's law. Each one has a worked solution and a mark scheme showing where the marks go.