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🔬 Biology  ·  Excretory Products and their Elimination  ·  NEET

In the urea cycle, urea is formed by combining ammonia with:

Answer: Carbon dioxide.

  • A Oxygen gas
  • B Glucose sugar
  • C Carbon dioxide
  • D Lactic acid

Correct answer: C. Carbon dioxide

Explanation: In the liver's ornithine (urea) cycle, ammonia is combined with carbon dioxide to make the less toxic urea.

The Nephron: Stages of Urine FormationBowman'scapsuleFILTRATIONPCTbulk REABSORPTIONLoop of Henlecounter-current - concentrates medullaDCTSECRETIONCollecting ductADH acts HERE

Filtrate flows through four functionally distinct stages of the nephron: Bowman's capsule filters blood, the PCT reabsorbs most useful substances unconditionally, the Loop of Henle builds a concentration gradient via counter-current exchange, the DCT secretes selected substances, and the collecting duct performs the final ADH-controlled water reabsorption.

Concept context

Nitrogenous waste, kidney structure, urine formation in the nephron, and hormonal regulation of excretion.

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