Water flows over the gills of a fish while blood flows through capillaries inside the gills.
The table shows the concentrations of respiratory gases before gas exchange takes place.
| respiratory gas | concentration in water entering the gills in mmol dm⁻³ | concentration in blood arriving at the gills in mmol dm⁻³ |
|---|---|---|
| oxygen | 0.30 | 0.08 |
| carbon dioxide | 0.05 | 1.10 |
Explain the directions of net diffusion of oxygen and carbon dioxide, and how a decrease in water flow over the gills would affect the rate of oxygen 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.