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It is responsible for the final step of aerobic respiration, where electrons generated by the breakdown of glucose are passed through various protein complexes, resulting in the production of ATP. The ETC consists of four main protein complexes (I, II, III, and IV) that are embedded within the inner mitochondrial membrane, as well as two mobile carrier molecules (coenzyme Q and cytochrome c). Each complex plays a specific role in the transport of electrons and the pumping of protons across the membrane. During the electron transport process, electrons are transferred from NADH and FADH2 (reduced forms of nicotinamide adenine dinucleotide and flavin adenine dinucleotide) to complex I and II, respectively. From there, the electrons pass through a series of redox reactions, with intermediate carriers such as coenzyme Q and cytochrome c, before reaching complex IV. At complex IV, the electrons are finally transferred to molecular oxygen, which combines with hydrogen ions to produce water. As the electrons move through the ETC, energy is released, which is used by the protein complexes to pump protons from the mitochondrial matrix to the intermembrane space, creating a proton gradient. This gradient is then used by ATP synthase, located on the inner membrane, to generate ATP through a process called oxidative phosphorylation. Defects or dysfunctions in the electron transport chain can lead to various mitochondrial disorders and diseases, as ATP production is disrupted. Additionally, the ETC is a target for certain drugs and toxins that can inhibit specific complexes, affecting cellular respiration. In summary, the electron transport chain is a critical component of cellular respiration, playing a key role in the production of ATP. It is a complex process involving multiple protein complexes and mobile carriers, and dysfunctions in this pathway can have significant consequences for cellular energy production.