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The main nitrogenous waste formed in the human body:
Topic: Urea as the main nitrogenous waste
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Answer
(b) Urea.
UREA is the chief nitrogenous waste in humans. It is formed IN THE LIVER from excess amino acids and excreted by the kidneys in urine.
WHY THE BODY MAKES IT: excess amino acids cannot be stored, so their amino group is removed (deamination), producing AMMONIA, which is highly toxic. The liver converts it at once into urea, which is far less toxic and can travel safely in the blood.
All four options are genuine nitrogenous wastes, so the question turns on which is the MAIN one. The pattern depends on water supply: AMMONIA — most toxic, needs much water to dilute; excreted by FISHES, which live in water UREA — moderately toxic; MAMMALS, including humans URIC ACID — least toxic, almost insoluble, needs least water; BIRDS, REPTILES and INSECTS
Land animals that must conserve water excrete the least soluble waste — which is why birds produce a white paste rather than liquid urine.
Urea.