A baker mixes yeast with flour, sugar and water to make bread dough. The dough is left in a warm place and it rises. Which statement explains why the dough rises?
The yeast produces ethanol gas, which fills spaces in the dough.
The yeast produces carbon dioxide gas in anaerobic respiration.
The yeast produces oxygen gas when it respires in the dough.
The yeast produces lactic acid, which makes the dough expand.
113 exam-style questions on OCR GCSE Biology 1.3 Respiration, covering 1.3.1 Cellular respiration supplies ATP, 1.3.2 Aerobic and anaerobic respiration, 1.3.3 Sugars and carbohydrates, 1.3.4 Amino acids and proteins, and 1.3.5 Fatty acids and lipids. Each one has a worked solution and a mark scheme showing where the marks go.