Is Reduction Exergonic Or Endergonic?

Is Reduction Exergonic Or Endergonic? The dehydrogenase enzyme reduces acetaldehyde to ethanol, which is an endergonic (energy-requiring) reaction: The reduction of acetaldehyde is coupled to the oxidation of NADH to NAD+, which is an exergonic reaction. How can you tell if a reaction is endergonic or exergonic? Exergonic reactions are also called spontaneous reactions, because