Biochemistry

formed. Under the influence of the enzyme catalase, hydrogen peroxide breaks down into water and molecular oxygen. The active part of the FAD molecule is the isoalloxazine ring of riboflavin, to the nitrogen atoms of which two hydrogen atoms can be attached, i.e. two electrons and two protons with the corresponding intramolecular rearrangement of double bonds. In addition to FAD, its phosphorylated derivative of FADF, which contains an additional phosphoric acid residue attached to ribose, is involved in redox reactions. In all these compounds, the starting substances are vitamins that must be ingested as part of food so that the fundamental process of biological oxidation is not disturbed - the main source of energy for vital processes. The next enzyme that catalyzes the transfer of hydrogen atoms from reduced flavonucleotides is coenzyme Q , or ubiquinone, a compound close to vitamin K. Coenzyme Q mediates between FAD H 2 and cytochromes. It is a benzoquinone derivative with a long side chain, which consists of 10 isoprenoid units (Co Qio). Coenzyme Q (oxidized form) Coenzyme Q (reduced form) The reduced form of flavin dehydrogenase enzymes in respiratory chain transmits hydrogen atoms (electrons and protons) CoQ . By adding hydrogen, ubiquinone from the oxidized form is converted to reduced. 108