Question

Microbiology Question:

An organism is exposed to a chemical which impedes (but does not block) the flow of electrons through the electron transport chain. Explain the consequences in a manner which demonstrates your understanding of chemiosmosis/oxidative phosphorylation.

Answer 1

In electron transport chain, the underlying concept is that the high energy electrons are donated by molecules like NADH and this energy of the electrons is utilised by complex I, complex III and complex IV to pump protons from the lumen to the intermembrane space against the concentration gradient. Thus, the energy of electrons is converted into the electrochemical potential of the proton gradient across the inner membrane of mitochondria. When the protons finally flow down their concentration gradient (chemiosmosis) via ATP synthase, the ATP synthase enzyme couples this process to the synthesis of ATP from ADP and Pi. The electrons finally end up reducing oxygen into water.

When a chemical impedes (but doesn't) the flow of electrons, the overall rate of the process of electron transport and oxidative phosphorylation gets slowed down. That is to say, the rate at which the electrons get transported through the complexes to build the proton gradient and the final formation of ATP and water gets slowed down. Hence, compared to the condition of no impeding chemical, the pace of the overall process is slowed down. However, since the chemical is not blocking the flow of electrons, there is no overall loss if the parameter of time (that it, the rate of the process) is ignored.

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