It all comes down to the first electron

Wed, 12 Jan 2022 22:42:12 GMT
Space Daily

Zurich, Switzerland (SPX) Jan 13, 2022 Every living thing requires energy. This is also true of...

How do the electrons get from respiration in the cells to the iron oxides which are found outside the cells? For this process microorganisms can use special molecules that receive two electrons at the cell surface, and then transport them to the iron oxides like a taxi.

There the two electrons alight from the taxi, and reduce trivalent iron in oxides to its divalent form.

These extracellular electron shuttles have been known about for a long time.

"In our relationship, we didn't look at the average energy of the two transported electrons as has been done up to now, but rather at the individual energy level of each electron," reports Meret Aeppli, lead author of the study.

Eawag-environmental chemist Thomas Hofstetter adds: "It turns out that the transfer of the first electron from the EES to the iron oxide is often decidedly less energetically efficient than the transfer of the second."

The researchers have shown that the energy difference between the first electron transferred from the EES to the iron oxide determines the iron reduction rate.

Michael Sander from the ETH Zurich explains the process with an analogy: "Under many conditions, the first electron is actually very reluctant to leave the EES taxi, but it is pushed out from the back seat, so to speak, by the second electron."

Electron transfer made visible using UV light To arrive at their findings, the authors of the study not only devised their own experiments and to collected the resulting data, but also integrated the results of previous studies.

The rate of electron transfer from the EES to the iron oxide, and thus the efficiency of the electron transport, can be made visible with UV light.

Research Report: "Thermodynamic controls on rates of iron oxide reduction by extracellular electron shuttles".