What happens to NADH and FADH2 during the electron transport chain?

During the electron transport chain, NADH and FADH2 serve as electron carriers that transport electrons derived from metabolic processes, such as glycolysis and the Krebs cycle, to the chain. As they pass through various complexes in the electron transport chain situated in the inner mitochondrial membrane, NADH donates electrons and is oxidized back to NAD+, while FADH2 is also oxidized back to FAD.

This process is crucial because the oxidation of NADH and FADH2 allows for the release of energy that is utilized to pump protons across the mitochondrial membrane, creating a proton gradient. This gradient ultimately drives the synthesis of ATP through oxidative phosphorylation via ATP synthase. Therefore, the regeneration of NAD+ and FAD is an essential part of the cellular respiration process, allowing these coenzymes to participate in metabolic cycles again, supporting ongoing ATP production.

The other options do not accurately describe the role of NADH and FADH2 in the context of the electron transport chain. They neither produce glucose nor directly inhibit the Krebs cycle; instead, they are vital for the continuation of the cycle by replenishing oxidized forms of the coenzymes.