Question

NAD+ and FAD are created from certain B vitamins that you obtain in your diet. Although NAD+ and FAD are needed in abundance for your daily cellular respiration needs, the amount of the precursor vitamins you require is not very large at all. Why would this be?

Answer 1

Question

The precursor for the NAD+ is niacin and FAD+ is riboflavin and also from some amino-acid. We need very small amount of vitamins in our diet and each vitamins are needed in milligrams(mg). But the NAD+ and FAD are required in very large amount. This difference in the amount of their precursor vitamins (niacin , riboflavin) and NAD+ , FAD is due to the fact that each precursor is just a raw-materials that follows many pathways with many steps to generate NAD+ and FAD. Each pathway generate different amount of NAD+ and FAD

The NAD+ is synthesized from three metabolic pathways. One is salvage pathway and second pathway is denovo pathway and third is Preiss-Handler pathway. These pathways generate high amount of NAD+ from small amount of vitamins and amino-acid. Therefore, although precursor is required in small amount, NAD+ is formed from many pathways and also NAD+ are regenerate in many metabolic pathways. Similarly, FAD is made from precursor riboflavin vitamin and ATP and also regenerated from other metabolic pathway , so that it is formed in high amount in humans.

Figure: Syntheis pathway of NAD+