A student uses a sensitive microcalorimeter to monitor the metabolic activity of germinating seeds (Pisum sativum). They record a continuous rise in the temperature of the insulated chamber, indicating that respiration is occurring. Which statement correctly explains this observation in terms of the thermodynamics of respiration?
Respiration is exothermic because the energy required to break the chemical bonds in glucose and oxygen is less than the energy released when new bonds form in carbon dioxide and water, resulting in a net release of thermal energy.
Respiration is endothermic because the activation energy required to initiate glycolysis absorbs thermal energy from the surroundings, resulting in a net decrease in temperature.
Respiration is exothermic because the synthesis of ATP from ADP and inorganic phosphate (PiP_iPi) is a highly exergonic reaction that directly releases heat to the surroundings.
Respiration is endothermic because the oxidation of glucose is coupled to the synthesis of ATP, which requires a net absorption of thermal energy from the surroundings.
16 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.