I suppose I dont really understand WHY they’re tied together. As electrons pass across the chain, does it just create energy to push the protons from the N to P side?
I suppose I dont really understand WHY they’re tied together. As electrons pass across the chain, does it just create energy to push the protons from the N to P side?
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Yes. Moving an electron from where it is to a new place where it will be more stable than where it came from releases energy. Wikipedia says “The flow of electrons through the electron transport chain is an exergonic process. The energy from the redox reactions creates an electrochemical proton gradient that drives the synthesis of adenosine triphosphate (ATP).”
My understanding is that the cytochromes of the ETC harvest the energy of the electrons by passing it from one reaction to the next. This energy is used to pump the protons across the cristae of the mitochondria, setting up the electrochemical gradient required to use ATP synthase. This is Reddit, so someone will certainly correct me if I’ve gotten this wrong.
Electron flow is coupled to proton translocation through conformational changes in the transmembrane protein. Protons are carried through amino acids and water as they accept and donate protons (behaving as acids and bases), and electrons quantum tunnel through mobile redox cofactors like cytochrome c and also stationary redox centers in the protein (such as bound cytochromes). For example, electron movement to one redox center can make that part more negatively charged, altering the local electric field, causing movement of a nearby charged amino acid. The new position of the amino acid then allows it to be part of a Grothuss chain to carry protons. The system is then reset when the electron moves to the next center. Although researchers have uncovered bits and pieces, the precise timing and path of electrons and protons is still under active investigation in the main three complexes (I, III, IV), not to mention other ETC systems. It’s a challenging topic because the mechanism involves conformational change, so you’d need to capture multiple conformations in structural studies. Molecular modelling is also proving useful, for example, to predict which amino acids are close enough to be reasonable to be part of the Grothuss chain.