1) The active group of both coenzymes (flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)) is flavin, which has a conjugated system of three rings, which, when reduced, can take two electrons and two protons. FAD consists of FMN associated with AMP. Typically, both compounds are covalently linked to enzymes. Both compounds are functionally close coenzymes. FAD and FMN are coenzymes of dehydrogenases. These enzymes catalyze cleavage from a hydrogen substrate, i.e. participate in oxidation – reduction reactions.
2)Coenzymes NAD and NADP are formed by nicotinamide and adenine associated with ribofuranose N-β-glycosidic bond. NADP differs from NAD by the content of another phosphoric acid residue attached to the hydroxyl of one of the D-ribose residues. The biological functions of NAD + and NADP + are different: the role of NAD + is more associated with energy processes in the cell, and NADP + is associated with plastic exchange reactions.