1. NADH (Nicotinamide adenine dinucleotide): NADH carries electrons from glycolysis and the Krebs cycle to the electron transport chain, where they are used to generate ATP.
2. FADH2 (Flavin adenine dinucleotide): FADH2 also carries electrons from the Krebs cycle to the electron transport chain, but it enters at a lower energy level than NADH, so it contributes to the generation of fewer ATP molecules.
Both NADH and FADH2 are reduced forms of their respective molecules, NAD+ and FAD. They gain electrons during the breakdown of glucose in cellular respiration, and then donate these electrons to the electron transport chain to generate ATP.
