NAD, NADH and NADP are
(a) not a participant in any catalytic reaction
(b) participants as cofactors in non-catalytic reaction
(c) participants as cofactor in enzyme catalysed reactions
(d) participants as cofactor in both non-catalytic and enzyme catalysed reactions.
(c) NAD and NADP are coenzymes for many oxidoreductase enzymes. The nicotinamide nucleotide play a widespread role as coenzymes to many dehydrogenase enzymes occurring both in the cystol and within the mitochondria. They are therfore key components of many metabolic pathways affecting carbohydrate, lipid and amino acid metabolism.