試題詳解

20. Which of the following statements about nitrogen metabolism in biological systems is INCORRECT?
(A) The enzyme glutamine synthetase catalyzes the ATP-dependent conversion of glutamate and ammonia to glutamine, serving as a key regulatory point in nitrogen assimilation.
(B) The urea cycle is the primary pathway for nitrogen excretion in most terrestrial vertebrates, converting ammonia into urea for safe excretion.
(C) Nitrogen fixation by nitrogenase requires ATP and is inhibited by molecular oxygen due to the enzyme's oxygen sensitivity.
(D) Nitrate reductase and nitrite reductase are exclusively found in prokaryotes and play a critical role in reducing nitrate to ammonia for assimilation.
(E) Aminotransferases (transaminases) use pyridoxal phosphate (PLP) as a cofactor to transfer amino groups between amino acids and a-keto acids, linking amino acid metabolism with the citric acid cycle.