NANP Board Practice Exam

Which cycle is responsible for disposing of nitrogen from amino acids during degradation?

1. BCAA cycle

2. Krebs cycle

3. Urea cycle

4. Glucose-alanine cycle

The correct answer is: BCAA cycle

The cycle that is primarily responsible for disposing of nitrogen from amino acids during degradation is the urea cycle. The urea cycle, also known as the ornithine cycle, plays a crucial role in the detoxification of ammonia that is produced during the breakdown of amino acids. It converts ammonia, which can be toxic in high concentrations, into urea, which is then excreted in urine. On the other hand, while the BCAA (branched-chain amino acid) cycle involves the metabolism of specific amino acids, it does not specifically focus on the disposal of nitrogen. The Krebs cycle, also known as the citric acid cycle, is primarily involved in the oxidation of carbohydrates, fats, and proteins to fuel cellular respiration, not directly in nitrogen disposal. The glucose-alanine cycle pertains to the transport of amino groups from muscle to the liver, but again it does not primarily handle the excretion of nitrogen as effectively as the urea cycle. Thus, the correct association is with the urea cycle, which is essential for safely removing excess nitrogen from the body.