Hello,
The electrons carried by NADH and FADH2 go through something called the electron transport chain; the electrons are donated through a chain, where they lose energy through every molecule it passes through. The energy is used to power hydrogen ions OUT of the mitochondria's inner compartments; this creates a concentration gradient, where the H+ ions diffuse back in. By diffusing back in, the carrier protein that it diffuses through makes ATP. On average, ETC makes 32 ATP. When the electrons are used up, they bind with hydrogen ions and oxygen molecules. This results in water- H2O. Oxygen is the final electron acceptor, and water is a waste product.
Faith xoxo