|
In most cases, glucose is oxidised in the presence of oxygen to give carbon dioxide. Thus, for respiration, an organism has to take in oxygen and give out carbon dioxide. This is called gaseous exchange. The oxygen taken in is used to break down the respiratory substrate (e.g., glucose) and energy is released along with carbon dioxide. This whole process is called respiration.
Gaseous exchange involves movements of some specialised structures. The mechanism of taking in oxygen and giving out carbon dioxide is called breathing. Thus breathing and respiration are not synonymous. Respiration involves the mechanical and the bio-chemical processes whereas breathing is only the mechanical or physical process of exchange of gases.
| 
