What is the electron transport chain?

The electron transport chain (ETC) is a sequence of protein complexes and electron carriers embedded in the inner mitochondrial membrane. These complexes pass electrons derived from NADH and FADH2 (produced in earlier metabolic pathways like glycolysis and the Krebs cycle) through a series of redox reactions. The energy released from these reactions pumps protons across the membrane, creating an electrochemical gradient used to generate ATP.