So things like nitrogenous, nucleotide bases, amino acids, glucose molecules. Because we have the oxalo acetate in the citric acid cycle that we can use to form glucose via gluconeogenesis, we also form things like porphyrin molecules. Remember that porphyrin is the organic carbon based component of heme groups used by things like hemoglobin proteins and my global protein. So the citric acid cycle is a very important cycle. It's the center of aerobic cellular respiration, of glucose metabolism. So the citric acid cycle functions to provide a means by which any fuel molecule so what is a fuel molecule?