Citrate is the first intermediate of the citric acid cycle and tricarboxylic acid (TCA) cycle. It also plays an important role in fatty acid synthesis which takes place in the cytoplasm. The movement is assisted by two enzymes, citrate-condensing enzyme, which catalyzes the condensation of the acetyl unit with oxaloacetate in the mitochondria, and citrate-cleavage enzyme (citrate lyase), which catalyzes the release of the acetyl radical in the cytoplasm of the cell. The citrate test detects the ability of an organism to use citrate as the sole source of carbon and energy. The medium contains citrate as the sole carbon source and inorganic ammonium salts (NH4H2PO4) as the sole source of nitrogen.