The chief nitrogenous waste product of humans is
Correct answer: B. urea
- A. ammonia
- B. urea
- C. uric acid
- D. creatine
Explanation
Surplus amino acids are deaminated in the liver and the toxic ammonia produced is converted at once into far less toxic urea by the ornithine cycle, which the blood then carries to the kidney. Ammonia is too poisonous to accumulate and is excreted directly only by animals surrounded by water, such as bony fish. Uric acid is the main waste of birds, reptiles and insects.
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About Excretion
Excretion removes metabolic wastes such as carbon dioxide, urea and excess salts, and differs from egestion, which removes undigested food. Questions cover kidney structure, nephron ultrafiltration, selective reabsorption and urine formation, along with the excretory roles of the lungs, skin and liver in maintaining homeostasis.
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