After NAD+ and FAD deliver their high-energy electrons to the electron transport chain (ETC) during cellular respiration, they are converted back to their oxidized forms: NAD+ and FAD. This process usually occurs in the mitochondria of eukaryotic cells.
NAD+ and FAD play a crucial role as electron carriers; they accept electrons during metabolic processes like glycolysis and the Krebs cycle. When they drop off the electrons, they release energy that is used to pump protons across the mitochondrial membrane, creating a proton gradient. This gradient ultimately drives ATP synthesis through oxidative phosphorylation.
After releasing the electrons, NAD+ and FAD can return to their respective pathways to pick up more electrons. This recycling is essential for the continuous flow of energy throughout the cell, ensuring that the metabolic processes can keep running efficiently.