Question

multiple choice question
in a pathway called the urea cycle, the liver combines ______ with carbon dioxide to produce urea, a less toxic waste.

ammonia
uric acid
oxygen
pyruvate

Explanation:

In the urea cycle, the liver processes ammonia (a toxic by - product of protein metabolism) by combining it with carbon dioxide to form urea, which is less toxic and can be excreted. Uric acid is related to purine metabolism and excretion in some organisms, oxygen is involved in respiration, and pyruvate is a product of glycolysis, so they are not involved in the urea cycle's reaction to form urea.

Answer:

A. ammonia