What is the role of NADH and FADH2 in respiration?

NADH and FADH₂ are key electron carriers in cellular respiration that transport high-energy electrons to the electron transport chain for ATP production.

During glycolysis and the Krebs cycle, electrons are removed from glucose-derived intermediates and transferred to NAD⁺ and FAD, converting them into NADH and FADH₂. These molecules store the captured energy in the form of high-energy electrons.

In oxidative phosphorylation, NADH and FADH₂ donate these electrons to the electron transport chain located in the inner mitochondrial membrane. As electrons pass through a series of protein complexes, their energy is released and used to pump protons across the membrane, creating a proton gradient.

This gradient drives ATP synthesis through ATP synthase. NADH contributes more to ATP production because it donates electrons at an earlier stage in the electron transport chain, resulting in a larger proton gradient compared to FADH₂.

After donating electrons, NADH and FADH₂ are converted back into NAD⁺ and FAD, which can be reused in earlier stages of respiration.

Overall, NADH and FADH₂ act as essential energy carriers, linking earlier metabolic pathways to ATP generation in oxidative phosphorylation.