The electron transport chain (ETC) is a crucial component of cellular respiration, located in the inner mitochondrial membrane. It consists of a series of protein complexes that facilitate the transfer of electrons from electron donors, such as NADH and FADH2, to electron acceptors. This process generates a proton gradient across the membrane, which is essential for ATP production. The proton gradient drives ATP synthase, an enzyme that synthesizes ATP from ADP and inorganic phosphate. Each NADH molecule can yield approximately 3 ATP, while each FADH2 yields about 2 ATP. When accounting for all the NADH and FADH2 produced during glycolysis, the citric acid cycle, and other metabolic processes, the total ATP yield from the electron transport chain and oxidative phosphorylation can reach up to 38 ATP molecules, making it a highly efficient energy production pathway.