glycerol--phosphate gets converted back to dihydroxyacetone phosphate by an inner membrane-bound mitochondrial glycerol--phosphate dehydrogenase  gpdh-m this time reducing one molecule of enzyme-bound flavin adenine dinucleotide fad to fadh fadh then reduces coenzyme q ubiquinone to ubiquinol which enters into oxidative phosphorylation this reaction is irreversible