An experiment was set up to investigate the temperature changes during the germination of mung bean seeds. Two vacuum flasks were prepared:
- Flask A contained germinating mung bean seeds.
- Flask B contained mung bean seeds that had been boiled (to kill them) and then washed in a mild disinfectant solution before being placed in the flask.
The flasks were sealed with cotton wool plugs, and a temperature probe was inserted into each flask to record the temperature over 5 days.
The graph shows the results of this experiment.
Which statement provides the correct explanation of these results?
Respiration in Flask A is an endothermic reaction that absorbs thermal energy from the surroundings, whereas Flask B remains constant because the dead seeds cannot absorb energy.
Respiration in Flask A is an exothermic reaction that releases heat energy during the breakdown of respiratory substrates; Flask B remains at constant temperature because the seeds are dead and the disinfectant prevents microbial respiration.
The temperature rise in Flask A is caused by photosynthesis, which is highly exothermic in young germinating seeds; Flask B remains at a constant temperature because boiling denatures the photosynthetic pigments.
Respiration in Flask A is an exothermic reaction; Flask B remains constant because boiling denatures the respiratory enzymes, but the disinfectant is unnecessary as microorganisms cannot metabolise boiled tissues.