* NADH: Nicotinamide adenine dinucleotide (NADH) is reduced to NADH during glycolysis and the Krebs cycle. It carries high-energy electrons and protons (H+) to the electron transport chain.
* FADH2: Flavin adenine dinucleotide (FADH2) is reduced to FADH2 during the Krebs cycle. It also carries high-energy electrons and protons (H+) to the electron transport chain.
These carriers deliver the electrons to the electron transport chain, where they are passed from one protein complex to another, releasing energy along the way. This energy is used to pump protons across the mitochondrial membrane, creating a proton gradient that drives the production of ATP, the cell's energy currency.
