During the electron transport process, which cofactor is utilized by Complex I?

Complex I of the electron transport chain, also known as NADH:ubiquinone oxidoreductase, primarily utilizes FMN (flavin mononucleotide) as a cofactor. During the process, electrons from NADH are transferred to FMN, which is then reduced to FMNH2. This step is crucial because it helps initiate the transfer of electrons through the complex towards coenzyme Q (ubiquinone), facilitating subsequent proton pumping and contributing to the establishment of the proton gradient that is crucial for ATP synthesis.

FMN plays a vital role in this process because it can accept and donate electrons, effectively functioning as a mediator between the now-reduced NADH and the further electron carriers in the chain. Its ability to exist in multiple oxidation states enhances its suitability for this rapid electron transfer, supporting the overall efficiency of cellular respiration and energy production.