The electron transport chain is the third and final step of cellular respiration. In this stage, high-energy electrons are released from NADPH and FADH2. This electrons move along the electron transport chains located in the inner membrane of the mitochondrion.
It has a series of protein complexes in the mitochondrial membrane where electrons from donor molecules are transferred to these protein complexes. These electrons can be transferred by pumping hydrogen ions. The pumping of hydrogen ions generates the gradient required for the ATP synthase to produce ATP.
These are the protein complexes that are found in the mitochondrial membrane, NADH dehydrogenase, cytochrome b-c1, cytochrome oxidase, and ATP synthase. There are also two mobile carriers found in the mitochondrial membrane that help carries out the process and these are ubiquinone and cytochrome c.
The electron transport chain starts off with two electrons being passed from the NADH to the NADH dehydrogenase complex. This transfer involves the pumping of one hydrogen ion for each electron and these two electrons are transferred to ubiquinone. The ubiquinone then moves the electrons to the cytochrome b-c 1 and the electrons are transferred to cytochrome c. The electrons are then passed on to the cytochrome oxidase which requires four electrons. These four electrons interact with oxygen molecules and 8 hydrogen ions. The four electrons, four hydrogen ions, and oxygen molecules are combined to form two water molecules and the other four-hydrogen ions are pumped across the mitochondrial membrane. The pumping of hydrogen ions generates the gradient which is a requirement for the ATP synthase to create ATP.