Urea Cycle Ornithine Cycle — FRCA Primary MCQ
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Correct answer: A — Urea cycle (ornithine cycle)
The urea cycle (ornithine cycle) converts toxic ammonia from amino acid deamination to urea in the liver. Urea is water-soluble and excreted renally. The cycle requires: ornithine / citrulline / argininosuccinate / arginine (regenerating ornithine). Liver failure leads to hyperammonaemia and hepatic encephalopathy due to impaired urea synthesis.
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist