Gaseous Exchange

The term 'respiration' was coined by Pepys (1966). At its core, respiration is the biological oxidation of food substances - carbohydrates, proteins and fats - a process that consumes oxygen and releases carbon dioxide while producing usable energy. Whatever organic substance gets oxidised this way is called a respiratory substrate, and among these, glucose is by far the most common. Respiration works by breaking the carbon-carbon bonds in these complex organic molecules through oxidation, and the energy this releases is partly stored as ATP and partly given off as heat. Every living cell respires, in plants and animals alike, and the overall process is essentially the reverse of photosynthesis, consuming the very glucose and oxygen that photosynthesis builds up: C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy (686 kcal, or 2868 kJ, per mole of glucose). Depending on which respiratory substrate is being oxidised, Blackman classified respiration into two types: floating respiration, the common form that uses carbohydrate, fat or organic acid as substrate and produces …