The third step in cellular respiration is the electron transport chain (ETC). This process occurs in the inner mitochondrial membrane. During the electron transport chain, electrons are transferred through a series of protein complexes and other molecules. These electrons come from NADH and FADH2, which were generated in the earlier stages of cellular respiration (glycolysis and the citric acid cycle).
As electrons move through the chain, their energy is used to pump protons (H⁺ ions) from the mitochondrial matrix into the intermembrane space, creating a proton gradient. This gradient is used by ATP synthase to produce ATP as protons flow back into the matrix. Additionally, at the end of the electron transport chain, electrons are combined with oxygen (the final electron acceptor) and protons to form water.
Overall, the electron transport chain is crucial for the production of the majority of ATP generated during cellular respiration.
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