All organisms respire in order to release energy to fuel their living processes. The respiration can be aerobic, which uses glucose and oxygen, or anaerobic which uses only glucose.
Don't confuse respiration with breathing, which is ventilation. Respiration happens in cells.
Respiration is a series of enzyme-controlled reactions that are needed to convert the stored chemical energy in food into a useable form and in manageable amounts.
Respiration is only around 40 per cent efficient. As animals respire, heat is also released. In birds and mammals, this heat is distributed around the body by the blood. It keeps these animals warm and helps to keep a constant internal temperature.
Energy is used:
Germinating peas grow rapidly. This growth process requires a lot of energy for cell division, so the rate of respiration in germinating peas is high.
One way to measure the rate of respiration is to measure the heat produced in the process.
In Flask A - germinating peas
In Flask B - germinating peas which have been disinfected
In Flask C - boiled, disinfected peas
The germinating peas will produce the most heat. Peas will carry out respiration to release the energy needed for growth and heat energy is produced as it is an exothermic reaction. The peas are also covered in microbes which also respire producing heat.
The germinating peas which have been disinfected will produce less heat than Flask A. The peas will respire to grow but the microbes will have been killed by the disinfectant. This means there are fewer organisms respiring and so less heat produced.
This is the control experiment. In this experiment heat was not produced because the peas have been boiled to denature the enzymes which catalyse respiration. They were then disinfected to remove any microbes that might decompose the dead peas.