A membrane permeable to glucose separates solution X from solution Y in a model exchange system. Solution X is continuously replaced. A pump moves solution Y past the membrane.
The pump is switched off. Temperature, membrane surface area and membrane thickness remain constant.
| pump status | glucose concentration in solution X (mmol dm⁻³) | glucose concentration in solution Y beside the membrane (mmol dm⁻³) |
|---|---|---|
| running, just before being switched off | 9.0 | 4.0 |
| off for 5 minutes | 9.0 | 7.5 |
Explain how switching off the pump changes the rate of net diffusion of glucose and predict what will happen to this rate if the pump remains off for a long time. Use information from the table in your answer.
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.