Carbon dioxide produced by respiring cells diffuses out of a culture vessel through a gas-permeable membrane. The vessel is redesigned so that the total area of this membrane is 180% of its original value. The membrane thickness increases from 0.20 mm to 0.30 mm. The concentration difference across the membrane remains constant.
Fick's law gives the relationship:
rate of diffusion∝surface area×concentration differencemembrane thickness \text{rate of diffusion} \propto \frac{\text{surface area} \times \text{concentration difference}}{\text{membrane thickness}} rate of diffusion∝membrane thicknesssurface area×concentration differenceCalculate the rate of carbon dioxide diffusion through the redesigned membrane as a percentage of the rate through the original 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.