NEET Biology NEET PYQ-Excretory System In Animals

  • question_answer
    The principal nitrogenous excretory compound in humans is synthesized [AIPMT (S) 2010]

    A) in kidneys but eliminated mostly through liver

    B) in kidneys as well as eliminated by kidneys

    C)  in liver and also eliminated by the same through bile

    D) in the liver, but eliminated mostly through kidneys

    Correct Answer: D

    Solution :

    [D] In humans, the principal nitrogenous excretory compound (ie, urea) is synthesized in liver by omithine cycle. In liver, one molecule of \[C{{O}_{2}}\] is activated by biotin and .combines with two molecules of \[N{{H}_{3}}\] in the presence of carbamyl phosphate synthetase enzyme and 2ATP to form carbamyi phosphate and one molecule of \[{{H}_{2}}O\] is released. Carbamyl phosphate reacts with omithine and forms citrulline. Citrulline combines with another molecule of ammonia and form arginine that is broken into urea and omithine in the presence of an enzyme arginase' and water. \[2N{{H}_{3}}+C{{O}_{2}}\xrightarrow[{}]{Arginase}N{{H}_{2}}-CO-N{{H}_{2}}+{{H}_{2}}O\] urea is eliminated mostly through kidney as nitrogenous excretory product.

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