What is the primary physiological function of the urea cycle in the human liver?
Answer and explanation
Correct answer: D. Converting toxic free ammonia generated by amino acid catabolism into non-toxic urea for urinary excretion
Catabolism of dietary and structural amino acids releases toxic ammonium ions (NH4+), which can cause fatal encephalopathy. The hepatic urea cycle (operating partly in the mitochondrial matrix and partly in the cytosol) consumes ammonia, bicarbonate, and aspartate to synthesize non-toxic, highly water-soluble urea (carbamide), which enters systemic circulation and is excreted by the kidneys.
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