A muscle needs more energy during vigorous exercise. Its oxygen supply is not sufficient to meet this demand by aerobic respiration alone.
Which change allows the muscle to continue contracting?
more ethanol is made aerobically, using carbon dioxide
more lactic acid is made aerobically, using carbon dioxide
more glucose is broken down anaerobically, producing lactic acid
more glucose is broken down anaerobically, producing ethanol
98 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.