What are the reaction centers of the electron transport chain?

The reaction centers of the electron transport chain (ETC) are complexes embedded in the inner mitochondrial membrane (in eukaryotes) or the plasma membrane (in prokaryotes) that facilitate the transfer of electrons. These centers include Complex I (NADH dehydrogenase), Complex II (succinate dehydrogenase), Complex III (cytochrome bc1 complex), and Complex IV (cytochrome c oxidase). Each complex plays a crucial role in transferring electrons from electron donors to oxygen, while simultaneously pumping protons across the membrane to create an electrochemical gradient. This gradient ultimately drives ATP synthesis through ATP synthase.