Crucian carp are fish that live in ponds. In winter, the ponds can be covered by ice for several months and the water contains almost no oxygen.
In these conditions, the muscle cells of crucian carp respire anaerobically and produce ethanol instead of lactic acid. The ethanol diffuses out of the fish through the gills into the water.
Before winter, crucian carp store very large amounts of carbohydrate.
Explain why this is needed for the fish to survive the winter.
Suggest why producing ethanol instead of lactic acid is an advantage to the fish.
The temperature of the water under the ice is about 4 ∘C4\ ^\circ\text{C}4 ∘C.
Suggest how this low temperature helps the fish to survive.
42 exam-style questions on Edexcel GCSE Biology 8.3 Respiration, covering 8.3.1 Aerobic and anaerobic respiration. Each one has a worked solution and a mark scheme showing where the marks go.