Noah is a 3-year-old boy recently diagnosed with epilepsy. He presented to his pediatric advanced practice registered nurse (APRN) in a primary care clinic with 2 weeks of increased seizure activity after a medication change. Symptoms also included a sudden increase in lethargy, ataxia, and drowsiness. Test results showed elevated ammonia, liver function, and an abnormal electroencephalogram reading. Which cell organelle is not working properly?