Anaerobic respiration is the process by which incomplete oxidation of respiratory substrate takes place. In this case, it occurs in the absence of oxygen resulting the end products of ethyl alcohol and CO2 in plants and lactic acid (in animals) with very slight energy.
Anaerobic respiration is observed in certain bacteria, yeast and other fungi, endoparasites and animal muscles cells. It is also known as fermentation. The common reaction of anaerobic respiration is:
Features of Anaerobic Respiration
Phase of Anaerobic Respiration
There are two definite phases of anaerobic respiration:
1. Glycolysis: The first phase of anaerobic respiration is glycolysis in which 2 molecules of pyruvic acid and 4H+ are formed from a molecule of glucose from the same reaction of glycolysis(EMP pathway) found in aerobic respiration.
2. Fermentation: The second phase of anaerobic respiration is fermentation which consists of decarboxylation and reduction reactions converting the pyruvic acid into either ethyl alcohol with the evolution of carbon dioxide (CO2).
Ethanol Fermentation: Two steps involve in this process. At first pyruvic acid undergo carboxylation in the presence of pyruvic carboxylase enzyme and produce acetaldehyde and CO2. Then the acetaldehyde dehydrogenated by NADH2 into ethanol in presence of dehydrogenase enzyme.
- Lactic acid Fermentation: The pyruvic acid dehydrogenated by NADH2 into lactic acid in anaerobic condition of cell and in presence of dehydogenase enzyme. Beside anaerobes lactic acid is formed in muscle cell of higher animal. Higher plants do not produce any lactic acid.
Energetic of Anaerobic Respiration
Two molecules of NADH2 and two molecules of ATP are formed in glycolysis. During fermentation two molecules of NADH2 are used. Only two molecules of ATP are used to produce slight energy of 20 Kcal.
Application of Anaerobic Respiration
Various microorganisms take part in the fermentation process and produce highly useful end products. These useful end products make benefit to the mankind in many ways. Some notable fermentation activities in the industrial sectors are given below: