Which process in the liver detoxifies ammonia produced by gut bacteria?

• A. Glycolysis
• B. Urea cycle
• C. Beta-oxidation
• D. Gluconeogenesis

Answer: (B)

Detoxifying ammonia produced by gut bacteria happens in the liver through the urea cycle. Ammonia is highly toxic, so hepatocytes convert it into urea, a far less toxic and water-soluble molecule that can be carried in blood to the kidneys for excretion in urine. The process starts when ammonia combines with carbon dioxide to form carbamoyl phosphate in the mitochondria, then proceeds through a series of steps that build argininosuccinate and ultimately yield urea and regenerate the helper molecule needed to keep the cycle going. This is why the urea cycle is the primary means by which the body safely disposes of excess nitrogen from amino acids.

The other processes listed relate to different metabolic tasks: glycolysis breaks down glucose for energy, beta-oxidation degrades fatty acids for fuel, and gluconeogenesis synthesizes glucose from non-carbohydrate sources. None of these directly detoxify ammonia the way the urea cycle does.