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An electron transport chain (ETC [1]) is a series of protein complexes and other molecules which 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.
The chain of redox reactions driving the flow of electrons through the electron transport chain, from electron donors such as NADH to electron acceptors such as oxygen and hydrogen (protons), is an exergonic process – it releases energy, whereas the synthesis of ATP is an endergonic process, which requires an input of energy.
These electrons enter the electron transport chain of the mitochondria via reduction equivalents to generate ATP. The shuttle system is required because the mitochondrial inner membrane is impermeable to NADH, the primary reducing equivalent of the electron transport chain.
The electron transport chain oxidizes coenzymes NADH and FADH2. Protein synthesis makes use of mitochondrial DNA, RNA, and tRNA. [5] Regulation of processes makes use of ions (Ca 2+ /K + /Mg +). [6] Additional metabolites present in the matrix are CO 2, H 2 O, O 2, ATP, ADP, and P i. [1]
For instance, the electron transport chain and oxidative phosphorylation all take place in the mitochondrial membrane. [4]: 73, 74 & 109 In contrast, glycolysis, pentose phosphate pathway, and fatty acid biosynthesis all occur in the cytosol of a cell. [5]: 441–442
Water-splitting process: Electron transport and regulation. The first level (A) shows the original Kok model of the S-states cycling, the second level (B) shows the link between the electron transport (S-states advancement) and the relaxation process of the intermediate S-states ([YzSn], n=0,1,2,3) formation
This reaction takes place on the inner mitochondrial membrane, allowing FADH 2 to donate its electrons directly to coenzyme Q which is part of the electron transport chain which ultimately transfers electrons to molecular oxygen O 2, with the formation of water, and the release of energy eventually captured in the form of ATP.
The Arc system connects the electron transport chain to regulation of certain genes, allowing aerobic respiration to occur in the presence of oxygen and fermentation to take place when no oxygen is present. This is done through the connection of ArcB with quinones from the electron transport chain.