Question

How many citric acid cycle steps are catalyzed by dehydrogenase enzymes?

Answer 1

Answer:4

The steps are,

1.conversion of isocitrate to alpha ketoglutarate.

It is catalyzed by enzyme isocitrate dehydrogenase in which a molecule of NADH is generated. (It is a 2 step process both catalyzed by isocitrate dehydrogenase. In 1st step isocitrate is dehydrogenated to oxalosuccinate with NADH production. In 2nd step oxalosuccinate undergoes spontaneous decarboxylation to form alpha ketoglutarate catalyzed by same enzyme. If needed you can consider it as 2 steps instead of one.)

2.conversion of alpha ketoglutarate to succinyl CoA.

It is catalyzed by alpha ketoglutarate dehydrogenase which produces a molecule of NADH.

3.conversion of succinate to fumarate.

It is catalyzed by succinate dehydrogenase which produces a molecule of FADH2.

4.conversion of malate to oxaloacetate.

It is catalyzed by malate dehydrogenase which produces a molecule of NADH.