Flavoproteins are proteins that contain a nucleic acid derivative of riboflavin: the Flavin-Adenine Dinucleotide or FAD. This proteins acts as dehydrogenation catalysts in biological reactions inside the mitochondria. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Riboflavin (E101), also known as vitamin B2 or vitamin G, is an easily absorbed, water-soluble micronutrient with a key role in maintaining human health. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ...