Urea cycle occurs in:

Ans: c (Both) Ref: Vasudevan Sreekumari, 4th ed, p. 168; Lippincott, p. 253The first two reactions of urea cycle occur in mitochondria and the remaining 6 steps occur in cytosol.Citrulline enters cytoplasm and ornithine returns to mitochondria to combine with carbamoyl phos phate.* Mitochondrial enzymes are:1) CPS-I2) OTCCPS-II is a cytoplasmic enzyme.1) Used for pyramidine synthesis2) Uses glutamine for synthesis of carbamoyl Po4 instead of ammonia.Most important points about urea cycle defects:Features:Hyperammonaemia| blood glutamine|BUN.Symptoms:Lethargy, vomiting, hyperventilation, coma, respiratory failure.Causes: This can be due to defeciency of any enzyme in urea cycle, but mainly due to:a) CPS defeciency (No increase in uracil / orotic acid)b) OTC defeciency (Uracil and orotic acid level | in blood)