Out of 38 ATP molecules produced per glucose, 32 ATP molecules are molecules are formed from NADH/FADH₂ in

Out of 38 ATP molecules produced per glucose, 32 ATP molecules are formed from NADH/FADH₂ in the Respiratory chain.
NADH is the electron donor in this system. It initiates the electron transport chain by donating electrons to NADH dehydrogenase.
NADH is oxidized to NAD in this process. Complex II oxidizes FADH, garnering still more electrons for the chain. At complex III, no additional electrons enter the chain, but electrons from complexes I and II flow through it. When electrons arrive at complex IV, they are transferred to a molecule of oxygen.