So if we recall the citric acid cycle, there's a step in the citric acid cycle where we basically transform we oxidize succinate into fumerate. And in this process, we have an enzyme known as succinate dehydrogenase that essentially reduces the fad into fadh two. So, remember, fad is Flavin adenine dinucleotide, which is capable of actually receiving extracting those high energy electrons. So these two h plus ions and one electron from each one of these two bonds is extracted and placed onto the fad to form the fadh two. And actually, this sucks in. A dehydrogenase that is used by the citric acid cycle is found within complex two.