And actually, because of that, less ATP molecules will be formed from fadh two than from NADH. Now, the reason we mentioned fadh two is because complex one is actually complex two is actually responsible for extracting those electrons from fadh two molecules. Now, let's think back to the citric acid cycle. In the citric acid cycle, the step that allowed us to form the fadh two molecule is this step here. In this step, Succinate is oxidized into fumarate, and the fad molecule is reduced into fadh two. So these two H atoms, along with one electron each, are extracted.