NANP Board Practice Exam

The urea cycle is the correct answer because it plays a crucial role in the detoxification and removal of nitrogen from amino acids during their degradation. When proteins are broken down, amino acids are released, and their nitrogen-containing amino groups must be processed to prevent toxicity.

The urea cycle converts the excess ammonia, which is derived from the deamination of amino acids, into urea, which is then excreted in urine. This cycle takes place primarily in the liver and involves a series of enzymatic reactions that effectively transform ammonia into urea. Importantly, by converting harmful ammonia into urea, the urea cycle protects the body from the potentially lethal effects of accumulating ammonia.

Other cycles, such as the Krebs cycle, do not directly dispose of nitrogen. Instead, they are involved in energy production through the oxidation of acetyl CoA and play a role in the metabolism of organic substances, including carbohydrates and fatty acids. Similarly, while the glucose-alanine cycle is involved in the transportation of nitrogen from muscle to the liver, it does not execute the detoxification and excretion of nitrogen like the urea cycle does. The BCAA cycle focuses on the degradation of branched-chain amino acids but does not encompass the overall nitrogen disposal process