A freshwater fish lives in water that contains a very low concentration of sodium ions. The concentration of sodium ions in the fish's blood is about 300 times the concentration in the water around it. Special cells in the gills take up sodium ions from the water into the blood.
Name the process the gill cells use to take up the sodium ions.
Explain your answer to part a).
Suggest one feature you would expect to see if you looked at one of these gill cells with a microscope.
Give a reason for your answer.
The fish is moved into water containing a chemical that stops respiration in its cells.
Predict what happens to the concentration of sodium ions in the fish's blood.
Explain your answer.
58 exam-style questions on AQA GCSE Biology 1.3 Transport in cells, covering 1.3.1 Diffusion, 1.3.2 Osmosis, and 1.3.3 Active transport. Each one has a worked solution and a mark scheme showing where the marks go.