Urea Cycle Flashcards
What is the pneumonic for remembering the Urea Cycle?
Orange Coloured Cats Always Ask For Awesome Umbrellas
How many reactions are involved in the cycle part of the Urea Cycle?
4
What is the name of the key regulatory enzyme in the Urea Cycle?
Carbamoyl Phosphate Synthase I
What are the two intermediates in the production of carbamoyl phosphate from bicarbonate via carbamoyl phosphate synthase I in the Urea Cycle?
Carboxy Phosphate
then Carbamic Acid
What small molecules are needed in the conversion of bicarbonate to carbamoyl phosphate in the urea cycle? And what small molecule are produced?
Input: (NH4+ and CO2 = essentially NH3), 2ATP
Output: Pi and 2ADP
Where does the first stage of the Urea cycle take place?
in the mitochondria
Where does the second stage of the Urea Cycle take place?
Cystol (Cytoplasm)
Ornithine joins with carbamoyl phosphate in the Urea Cycle to produce what molecule and via which enzyme?
Citrulline via ornithine transcarbamoylase
What does citrulline combine with in the 2nd reaction of the cycle in the Urea Cycle?
Aspartate
What molecule is produced in the urea cycle after combining citrulline with aspartate? What enzyme undertakes this reaction?
Arginosuccinate via arginosuccinate synthase
What enzyme acts on Arginosuccinate once it is produced in the Urea Cycle and what two molecules are produced?
arginosuccinase
Fumarate and Arginine
What tow molecules are produced during the Urea Cycle due to Arginosuccinate Cleavage and what happens to these molecules?
Fumarate (by product used as a TCA intermediate)
Arginine (continues in the cycle for the 4th step)
What small molecule does arginine combine with in the (final) step of the Urea Cycle?
H2O
What two molecules are produced during hydrolysis of Arginine in the Urea Cycle? What happens to these two molecules?
Urea (excreted as a non-toxic form)
Ornithine (transported to the mitochondria continues in the Urea Cycle)
