Tuesday, December 13, 2011

Respiration in Microorganisms


Respiration is a catabolic process where the microorganisms convert biochemical energy from nutrients into Adenosine Tripohsphate(ATP). ATP is ultimately utilized by the cells for their energy requirements during motility, transport of nutrients across the membrane and for other anablic activities.

Microorganisms exhibit great diversity in metabolism. Some microbes(organotrophs) use organic carbon molecules such as sugar, amino acids and fatty acids and molecular oxygen for their respiration.

Others(lithotrophs) use inorganic molecules such as iron, sulfur, nitrate, methane,fumarate and acetate for their energy generation and uses elemental sulfur, Co2, Ferric iron etc… as Electron acceptors.

Microorganisms can carryout respiratory activities in different environments. Respiratory activity that use oxygen as final electron acceptor is called aerobic respiration and other than oxygen as final electron acceptor is called anaerobic respiration.

Under anaerobic conditions another respiratory activity also performed by the microorganisms namely Fermentation. It is the partial degradation of organic compounds to generate energy.

Microorganism like E.Coli can survive in the presence of oxygen and even in the absence of oxygen. In the oxygen presence they carry out aerobic respiration and in the absence of oxygen they carryout Nitrate respiration.

Aerobic respiration in microorganism is similar to the aerobic respiration in plants. This involves glycolysis, TCA cycle and electron transport system to generate energy. But there are variations in glycolysis.

Glycolysis is the breakdown of glucose into pyruate. It occurs in the cytoplasm of all the microbes(both procayotes as well as Eukaryotes). Microorganism use different pathways to to do this job. Plants use only EMP pathway to do this but Microorganisms use EMP a swell as  Entner-duodroff pathway and pentose phosphate pathway. Discussed eloberately in the article named “Breakdown of Glucoseto Pyruate”.

TCA Cycle is common pathway for plants and microorganisms to generate reducing power and is ultimately used to generate ATP in the Electron transport system. In eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion. Bacteria also use the TCA cycle to generate energy, but since they lack mitochondria, the reaction sequence is performed in the cytosol. Discussed elaborately in the article named “TCA Cycle”.

Electron transport system is simlar to the plants but very diverse from one microorganism to microorganism in the electron carriers. Electron transpot system occurs in the plasma membranes of bacteria. Discussed elaborately in the article named “Electron Transport System”.

Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen, via an electron transport chain. Discussed elaborately in the article named “Fermentation”.

Anaerobic respiration, is a cellular respiration that takes place without oxygen and begins the breakdown process using electron acceptors and instruments, but does not use oxygen. Discussed eloberately in the article named “Anaerobic Respiration”.

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