Hydrogencarbonate indicator is red when the carbon dioxide concentration is normal. It turns yellow when the carbon dioxide concentration increases. A student sets up two tubes of hydrogencarbonate indicator. Tube 1 contains living germinating seeds. Tube 2 contains boiled seeds. After one hour, the indicator in tube 1 is yellow. The indicator in tube 2 is still red. Which statement explains these results?
The living seeds released carbon dioxide as they respired.
The living seeds absorbed carbon dioxide as they respired.
The boiled seeds released oxygen as they photosynthesised.
The boiled seeds absorbed oxygen as they released energy.
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.