Respiration is the process of taking oxygen into the cells, using it to release energy from the digested food and eliminating the waste products (carbon dioxide and water).
Respiration involves two main processes:
Breathing or External Respiration:
The process of taking in oxygen-rich air from the surrounding medium and giving out carbon dioxide-rich air into the medium is called breathing or external respiration.
The process of breakdown of food molecules (mainly glucose) within the cells using oxygen to release energy is called cellular respiration. Carbon dioxide and water are produced as by-products. The energy released in this process is used by living organisms to carry out their life processes. Cellular respiration can be represented as follows-
Glucose + Oxygen ———–> Carbon dioxide + Water + Energy
The process of cellular respiration is quite similar to burning or combustion. However, there are several differences as well.
|It is a slow process.||It is a fast process.|
|Takes place at body temperature (37°C) inside body cells.||Takes place at a high temperature outside the body of a living organism.|
|Many steps are involved in the breakdown of food.||Fuel is directly converted into carbon dioxide and water.|
|The energy released is stored inside a chemical molecule.||Energy is released as heat and light.|
|Enzymes are needed to carry out the respiration process.||No enzymes are required.|
Respiration is a basic life activity and occurs in the cells of all living organisms. It is the process by which they obtain energy from the food they eat. Respiration is of following two types-
Most living organisms require oxygen for respiration. This type of respiration is known as aerobic respiration. The organisms may obtain the oxygen from air or water. In aerobic respiration, glucose is completely oxidized into carbon dioxide and water and a large amount of energy is released in the process.
Organisms exhibiting aerobic respiration cannot live in the absence of oxygen.
Some organisms like yeast and some bacteria do not require oxygen for their survival and can live in its absence. The type of respiration taking place in the absence of oxygen is called anaerobic respiration. This type of respiration releases a very small amount of energy. Glucose is incompletely broken down to ethyl alcohol and carbon dioxide. This process is also called alcoholic fermentation. Alcoholic fermentation is used in baking, preparation of wine, beer etc.