Urea cycle

Question 1

Where does urea cycle occur?

Answer 1

Cytosol
Mitochondria

Question 2

Outline urea cycle?

Answer 2

1) 1 ammonia enters cycle by transamination reaction to form glutamate (recycled by deamination)
NH3 moves into the mitochondria and reacts with HCO3- (with ATP) to form carbamoyl phosphate (enzyme = carbamoyl phosphate synthase)
Carbamoyl phosphate reacts with ornithine to form citrulline (enzyme = ornithine transcarbamylase)
Moves out into the cytoplasm through a transporter
Reacts with aspartate (and ATP) to form arginine succinate (enzyme = argininosuccinate synthase)
This breaks down into arginine and releases fumarate (enzyme = argininosuccinate lyase)
Arginine reacts with water to produce ornithine release urea (enzyme = arginase/ornithine aminotransferase)
Ornithine then re-enters the mitochondria to continue the cycle