Question

Bacteria can perform aerobic and anaerobic respiration depending on their enzymes and metabolic needs. A student argued that aerobic and anaerobic respiration should produce the same amount of ATP. He reasoned that they both use basically the same process; only the terminal electron acceptor is different. What is the primary error in this student’s argument? Think about the different organisms in the body and in nature. Discuss how some produce their energy by anaerobic and aerobic metabolism. Discuss what would be available to them in this environment and what would they use as a primary electron acceptor. Would they all produce the same amount of ATP (energy) ? Within your discussion, mention a specific bacteria that uses aerobic, or anaerobic, aerotolerant, facultative anaerobic metabolism etc. Include a link to your source not previously posted.   

Answer 1

ANSWER :-

1. There is a major similarity in the mechanisms of both anaerobic and aerobic microorganisms however, it should be pointed out that Electron Transfer chain acceptors vary for both these groups. Aerobic organisms tends to have oxygen as the terminal Electron acceptor producing water and is a potent source to charge the Electron Transfer Chain through the membrane generating a proton pump to produce ATP. This results in production of around 36-38 ATP molecule in total taking into consideration the processes of Glycolysis and Kreb's cycle which produced around 4 ATP. So, major production relies on the ATP yielding substrate and the reduced FAD+ and NAD+ Electron carriers that participate in the Electron Transfer Chain. Let's consider the example of Methanogenic bacteria which uses CO2 as the terminal electron scceptor anf generates a reduced form of Methane which is able to produce a net of 2 ATP molecule after the entire process is concluded taking into consideration net involvement and production of 2 Methane molecules. This shows the ATP output in case of anaerobic respiration is not potent as compared to aerobic respiration involving oxygen which effectively drives the ETC process.
2. It is not always the Electron Transfer Chain that will be followed. Let's consider the example of fermentation that occurs in the absence of oxygen as a continuation of Glycolysis. The end product is alcohol in case of Alcoholic fermentation and Lactate in lactic acid fermentation from pyruvate and the net yield of ATP is 2 in both the cases apart from the 2 ATP produced during Glycolysis. These responses are just to ensure that a short and quick energy is being provided at times when oxygen supply is not prominent.
3. There are various organisms that uses various strategies in order to carry out aerobic and anaerobic respiration. E.coli can be considered as a facultative anaerobe in which it can carry out the process of fermentation only when oxygen is not available to carry out the process of Kreb's cycle and ETC. To include one more point, I would add the presence of sulfate as electron scceptor. There is a net requirement of 2 ATP molecules for the activation of various electron acceptors involved which in turn reduces the overall yield of ATP.

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