Carbon dioxide diffuses from respiring muscle cells into nearby blood.
A scientist uses Fick's law to predict relative diffusion values for two samples of muscle tissue.
| Sample | Surface area of exchange membrane in mm2\mathrm{mm^2}mm2 | Dissolved carbon dioxide concentration in muscle cells in mmol dm−3\mathrm{mmol\,dm^{-3}}mmoldm−3 | Dissolved carbon dioxide concentration in arriving blood in mmol dm−3\mathrm{mmol\,dm^{-3}}mmoldm−3 | Effective membrane thickness in mm\mathrm{mm}mm |
|---|---|---|---|---|
| A | 80 | 1.30 | 1.00 | 0.0100 |
| B | 100 | 1.55 | 1.15 | 0.0125 |
Calculate the percentage increase in the relative diffusion value from sample A to sample B.
Use Fick's law to explain how the differences between sample A and sample B affect the predicted rate of carbon dioxide diffusion.
Blood flow through the capillaries near sample B increases. The surface area and membrane thickness do not change.
Explain how the increased blood flow could further increase the rate of carbon dioxide diffusion.
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.