Aug 22, 2010

Aerobic and Anaerobic Respiration

Respiration is one of the imperative functions of the body that are of crucial importance for all the living organisms be it human being, or the microscopic bacteria. In general the process of respiration serves two basic purposes in living organisms, the first one being disposal of electrons generated during catabolism and the second one being production of ATP. The respiration machinery is located in cell membranes of prokaryotes whereas it is placed in the inner membranes of mitochondria for eukaryotes. Respiration requires a terminal electron acceptor. Simply put, the respiration process, which uses oxygen as its terminal electron acceptor, is called aerobic respiration and the one, which uses terminal electron acceptors other than oxygen, is called anaerobic respiration.

Differences between Aerobic and Anaerobic Respiration
Starting from the bio-chemical pathway used to utilize bio-molecules, to the amount of energy produced in the respiration process, there exist a lot of differences between aerobic and anaerobic respiration. Let us discuss the two respiration processes separately with respect to the process, outcome and the chemical reactions involved in aerobic and anaerobic respiration.

Aerobic Respiration
Aerobic respiration is the process that takes place in presence of oxygen. Aerobic respiration is the metabolic process that involves break down of fuel molecules to obtain bio-chemical energy and has oxygen as the terminal electron acceptor. Fuel molecules commonly used by cells in aerobic respiration are glucose, amino acids and fatty acids.. The process of obtaining energy in aerobic respiration can be represented in the following equation:
Glucose + Oxygen →Energy + Carbon dioxide + Water

The aerobic respiration is a high energy yielding process. During the process of aerobic respiration as many as 38 molecules of ATP are produced for every molecule of glucose that is utilized. Thus aerobic respiration process breaks down a single glucose molecule to yield 38 units of the energy storing ATP molecules.

Anaerobic respiration
The term anaerobic means without air and hence anaerobic respiration refers to the special type of respiration, which takes place without oxygen. Anaerobic respiration is the process of oxidation of molecules in the absence of oxygen, which results in production of energy in the form of ATP or adenosine tri-phosphate. Anaerobic respiration is synonymous with fermentation especially when the glycolytic pathway of energy production is functional in a particular cell. The process of anaerobic respiration for production of energy can occur in either of the ways represented below:
Glucose (Broken down to) →Energy (ATP) + Ethanol + Carbon dioxide (CO2)

Glucose (Broken down to) →Energy (ATP) + Lactic acid

The process of anaerobic respiration is relatively less energy yielding as compared to the aerobic respiration process. During the alcoholic fermentation or the anaerobic respiration (represented in the first equation) two molecules of ATP (energy) are produced. for every molecule of glucose used in the reaction. Similarly for the lactate fermentation (represented in the second equation) 2 molecules of ATP are produced for every molecule of glucose used. Thus anaerobic respiration breaks down one glucose molecule to obtain two units of the energy storing ATP molecules.
 
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