Protein complex two is known as our succinate oxidore reductase. And succinate oxidore reductase basically contains our enzyme, the protein involved in the citric acid cycle. So we know that in the citric acid cycle we form our fadh two molecule, our electron carrier. And that fadh two molecule is formed directly in protein complex number two. So protein complex number two, our succinate oxidore ductase, forms fadh two. And then that fadh two basically releases our electrons and those electrons are picked up by our Ubiquinone molecule.