The electron transport chain (ETC) takes place in the inner mitochondrial membrane of eukaryotic cells. This membrane is highly folded into structures called cristae, which increase the surface area for the ETC to occur. The ETC is a crucial part of cellular respiration, where it helps in the production of ATP, the energy currency of the cell.
In prokaryotic cells, which lack mitochondria, the electron transport chain is located in the plasma membrane. Despite the difference in location, the fundamental process remains the same, involving the transfer of electrons through a series of protein complexes and other molecules to create a proton gradient that drives ATP synthesis.