Amino acid side chains that are in direct contact with NAD are outlined. Both compounds are bound to their respective enzymes by weak interactions. They take on a specific conformation, when binding to a pocket at the enzyme's surface. The signs change to the opposite, when the reaction runs the other way round. Accordingly, they do have to take it up with their vegetable nutrition.
Most vitamins function as coenzymes.
Since they are synthesized in plant cells, they should occur in the chapter about the molecular class they belong to. The active part of FAD is an alloxazin ring. In additin, FAD is bound covalently. After binding of these cofactors, the enzymes do take on a yellow colour. They are called flavoproteins.