A fish obtains oxygen by diffusion from water across its gills into its blood. A blockage reduces the flow of water over the gills. The surface area and thickness of the gills and the water temperature remain constant.
The table shows dissolved oxygen concentrations immediately before and immediately after the blockage occurs.
| Condition | Dissolved oxygen concentration in water beside the gills / mmol dm−3^{-3}−3 | Dissolved oxygen concentration in blood arriving at the gills / mmol dm−3^{-3}−3 |
|---|---|---|
| before blockage | 0.26 | 0.04 |
| after blockage | 0.14 | 0.04 |
Explain how the blockage affects the initial rate of oxygen diffusion into the blood and predict how this affects the oxygen supply to the fish's cells. Use the data 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.