So within this vertical component of complex one, we have Flavin mononucleotide, which accepts those two high energy electrons from the NADH molecule. Now, if we take a look at the structure of FMM, this is what it's going to look like in its fully oxidized form. So oxidized basically means before it accepted those electrons. So we have this r component that contains a phosphate group not shown here. And we have this three ring structure and this three ring structure. So one, two, three is known as the isoloxazine ring.