Via the transferred electrons, this energy is used to generate a proton gradient across the mitochondrial membrane by "pumping" protons into the intermembrane space, producing a state of higher free energy that has the potential to do work. Each reaction releases energy because a higher-energy donor and acceptor convert to lower-energy products. Each electron donor will pass electrons to an acceptor of higher redox potential, which in turn donates these electrons to another acceptor, a process that continues down the series until electrons are passed to oxygen, the terminal electron acceptor in the chain. The electron transport chain comprises an enzymatic series of electron donors and acceptors. At the inner mitochondrial membrane, electrons from NADH and FADH 2 pass through the electron transport chain to oxygen, which provides the energy driving the process as it is reduced to water. Most eukaryotic cells have mitochondria, which produce ATP from reactions of oxygen with products of the citric acid cycle, fatty acid metabolism, and amino acid metabolism. In bacteria, the electron transport chain can vary between species but it always constitutes a set of redox reactions that are coupled to the synthesis of ATP through the generation of an electrochemical gradient and oxidative phosphorylation through ATP synthase. Here, light energy drives electron transport through a proton pump and the resulting proton gradient causes subsequent synthesis of ATP. In photosynthetic eukaryotes, the electron transport chain is found on the thylakoid membrane. The energy released by reactions of oxygen and reduced compounds such as cytochrome c and (indirectly) NADH and FADH2 is used by the electron transport chain to pump protons into the intermembrane space, generating the electrochemical gradient over the inner mitochondrial membrane. In eukaryotic organisms the electron transport chain, and site of oxidative phosphorylation, is found on the inner mitochondrial membrane. It is this electrochemical gradient that drives the synthesis of ATP via coupling with oxidative phosphorylation with ATP synthase. The free energy released when a higher-energy electron donor and acceptor convert to lower-energy products, while electrons are transferred from a lower to a higher redox potential, is used by the complexes in the electron transport chain to create an electrochemical gradient of ions. In an electron transport chain, the redox reactions are driven by the difference in the Gibbs free energy of reactants and products. In anaerobic respiration, other electron acceptors are used, such as sulfate. In aerobic respiration, the flow of electrons terminates with molecular oxygen as the final electron acceptor. The energy from the redox reactions creates an electrochemical proton gradient that drives the synthesis of adenosine triphosphate (ATP). The flow of electrons through the electron transport chain is an exergonic process. Many of the enzymes in the electron transport chain are embedded within the membrane. The electrons that are transferred from NADH and FADH2 to the ETC involves four multi-subunit large enzymes complexes and two mobile electron carriers. Photosynthetic electron transport chain of the thylakoid membrane.Īn electron transport chain ( ETC ) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H + ions) across a membrane. It mediates the reaction between NADH or succinate generated in the citric acid cycle and oxygen to power ATP synthase. Energy-producing metabolic pathway The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes.
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