Anaerobic respiration is a process in which organisms produce energy in absence of oxygen. This BiologyWise article tells you about all the steps of anaerobic respiration in detail.
All living organisms need energy to perform various functions. This energy is obtained by a process known as glycolysis. Scroll down to acquaint yourself with the process of anaerobic glycolysis.
Glycolysis produces energy in the form of ATP. During the process, glucose gets oxidized to either lactate or pyruvate. There are two different pathways by which the glycolysis process takes place. One is aerobic and the other is anaerobic. Anaerobic glycolysis is a metabolic pathway involving the transformation of glucose to pyruvate and the further conversion of pyruvate to lactate, in the absence of oxygen.
This system is also known as the lactic acid system, as the end product is lactate, a conjugate base of lactic acid (conversion of pyruvate into lactate is brought about by the enzyme lactate dehydrogenase). It generally takes place when instant energy is required in the complete absence of oxygen or in a limited supply of oxygen. This pathway provides energy for a period ranging from 10 seconds to 2 minutes only.
The Lactic Acid System
» This form of glycolysis is the main source of energy in some plants and organisms. It is an important source of ATP during vigorous exercise when there isn’t an enough supply of oxygen.
» This pathway is active in bacteria involved in souring milk and formation of yogurt. It also exists in yeasts where pyruvate is first converted to acetaldehyde and carbon dioxide and then to ethanol in the absence of oxygen.
» There are two types of anaerobic fermentation processes that can occur in the absence of oxygen. They are lactic acid fermentation and alcoholic fermentation. Let us get some more information about these processes from the upcoming passages.
Lactic Acid Fermentation
➜ Lactic acid fermentation pathway is commonly seen in animal cells and in lactic acid bacteria. Animal tissues produce energy through this pathway.
➜ During this process, breakdown of glucose takes place in the absence of oxygen. Carbohydrate break down occurs in the cells and results in the formation of pyruvic acid and hydronium ions.
➜ The pyruvate further undergoes oxidation forming lactic acid, which then dissociates into lactate and H+. NADH gets oxidized in this whole process, which is the source of energy for the cells.
The reaction involved in the conversion of pyruvate into lactate can be represented as follows:
Puruvate + NADH + H+ → Lactate + NAD+
➜ The lactate produced diffuses out of the cell and passes into the liver. It is then converted to glucose which is capable of passing back into the peripheral cells to re-enter glycolysis. This forms a continuous cycle.
➜ The red blood cells obtain most of their energy through this process. However, excess lactic acid production can lead to lactic acidosis.
► This pathway generally takes place in organisms, like yeast and many plants. It involves the conversion of pyruvate into acetaldeyde and carbon dioxide which are further converted into ethanol.
► NADH is converted back to NAD+ and ethanol is the end product of this pathway. This process is employed in the manufacturing of alcoholic beverages and also in the biotechnology industry to generate carbon dioxide that is necessary for bread making.
The main difference between anaerobic and aerobic glycolysis is that the sugar is not broken down completely in the latter. Instead, it is converted to lactic acid or ethyl alcohol. However, a lot of animals and plants use the anaerobic pathway for ATP production.