Respiration is the process of oxidative breakdown of organic materials with the release of energy and change of Potential Energy into Kinetic Energy.
Respiration is a catabolic process as the breakdown of cellular substances with the liberation of energy takes place.
Respiratory Substrate : Respiratory substrate is the protoplasmic materials which on oxidation liberates energy. Glucose is the starting point of liberation.
Respiration Time : Process of respiration takes place on the whole day and night.
Sites of Respiration : There are two sites of respiration namely cytoplasm and mitochondria.
Oxygen Sources : Oxygen is obtained from environment for respiration.
Plants and Animals : Land plants and animals get oxygen from environment while aquatic ones get oxygen from dissolved water.
Types of Respiration : Respiration is of two types namely—
(i) Aerobic respiration and
(ii) Anaerobic Respiration
(i) Aerobic Respiration : It takes place in the living cells which require oxygen.
It is completed in two stages, i.e. (a) Glycolysis and (b) Krebs cycle. Chemical reation is as follows—
C6H12O6 + 6O2 6CO2 + 6H2O + 686 Kcal
Glycolysis is the biochemical change in which one molecule of glucose gets converted into 2 molecules of pyruvic acid.
Krebs cycle is the oxidative decarboxylation of pyruvic acid into CO2 and H2 atoms.
(ii) Anaerobic respiration : This kind of respiration takes place in anaerobic bacteria and in plant seeds.
Anaerobic respiration occurs in the organism which can live without oxygen.
In this respiration only glycolysis takes place due to the abscence of oxygen.
The reaction is
C6H12O6 2C2H5OH + 2CO2
Difference between Respiration and breathing
Respiratory Quotient (R.Q.) : R.Q. is defined as “the ratio between the volume of carbondioxide given out and oxygen taken in simultaneously, by a given weight of the tissue in a given period of time at standard temperature and pressure”.
Fermentation : The term fermentation is applied to several processes of oxidation carried out by some micro organisms like bacteria, yeast and fungi. Most of the fermentations are anaerobic but some are aerobic. In all these fermentations end products are formed by the incomplete oxidation of carbohydrates.
Economic Importance of Fermentation : Production of beer, vineger, alcohol, curd, lactic acid, etc. involves fermentation process. It is very useful to industries which produce these products.
