Answer: Electron transport chain is a final stage of aerobic cellular respiration that involves the formation of large amount of ATP ( adenosine triphosphate) that is the energy currency of the cell.
It takes place in the inner mitochondrial membrane. Electrons are passed through various protein complexes present in the inner mitochondrial membrane.
When this happens, protein complexes push protons from mitochondrial matrix to the inter-membrane space, creating a proton gradient outside. ATP synthase is a final protein complex that forms ATP using the concentration gradient of protons.