This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Which of the following is true in relation to the urea cycle \nSelect and explain. \nA. First 2 steps in mitochondria, B. Defect of enzyme of any step can cause deficiency disease, C. Citrulline is formed by combination of carbamoyl phosphate and L. Ornithine, D. All of these', 'role': 'user'}, {'content': 'Answer: D \nExplanation: First two steps of the urea cycle occur in mitochondria and remaining steps take place in the cytosol.\nDeficiency of any of the urea cycle enzymes would result in hyperammonemia.\nUrea is formed by NH3, aspartate (not glutamate) and CO2. In urea, nitrogen atoms are derived from NH3 and aspartate, and source of carbon is CO2.', 'role': 'assistant'}]