Well, in step six of glycolys, that's the beginning of stage three. We essentially take a molecule we call gap. So glyceroaldehyde three phosphate and we oxidize it into a molecule we call 13 BPG one three bisphosphoglyceride. And the enzyme that catalyzes this reaction is known as gap dehydrogenase. Now, for gap dehydrogenase to actually function, it must be able to use a coenzyme we call nicotine amide adenine Dinucleotide in its oxidized form, namely NAD plus. And if it can't use NAD plus, if for some reason the NAD plus is not available in a cell, this process will essentially stop.