Urea Cycle

Question 1

Site of Urea Cycle

Answer 1

LIVER

mitochondria and cytoplasm

Question 2

Urea cycle

Answer 2

Krebs Henseleit Cycle

Ornithine Cycle

Question 3

Conversion of body’s nitrogenous waste (ammonia) to urea

Answer 3

Urea cycle

Question 4

Substrates of Urea Cycle

Answer 4

NH3, aspartate, CO2

Question 5

Product of Urea Cycle

Answer 5

Urea

Question 6

Rate Limiting Step of Urea Cycle

Answer 6

nh3 + CO2 –> Carbamoyl phosphate

CARBAMOYL PHOSPHATE SYNTHETASE I

allosteric activator: N-ACETYLGLUTAMATE

Question 7

Reactions of Urea Cycle

Answer 7

1st 2 reactions - mitochondria

rest of reactions - cytoplasm

Question 8

Transporters of Urea Cycle

Answer 8

Ornithine Transporter - for ENTRY of ORNITHINE

Citrulline Transporter - for EXODUS of CITRULLINE

Question 9

Links amino nitrogen of aspartate to citrulline

ASPARTATE - provides 2nd nitrogen of urea

a ligase

Answer 9

Arginino Succinate Synthetase

REQUIRES ATP
2 inorganic phosphates are utilized

Question 10

Cleavage of arginosuccinate to arginine and fumarate

a LYASE

Answer 10

ARGININO SUCCINATE LYASE

Question 11

Hydrolytic cleavage of arginine, releases urea and reforms ornithine which reenter into mitochondria

a HYDROLASE

Answer 11

ARGINASE

Question 12

Enzyme which catalyzes the formation of N Acetyl Glutamate

Answer 12

N Acetyl Glutamate Synthase

Question 13

Amino acid that is produced in urea cycle

Answer 13

ARGININE

Question 14

Link between the urea cycle and krebs cycle

Answer 14

FUMARATE

Question 15

Has direct neurotoxic effect on the CNS

Answer 15

HYPERAMMONEMIA

tremors, slurring of speech, vomiting, blurring of vision
cerebral edema
somnolence, coma and death

Question 16

MC urea cycle disorder

Answer 16

Hyperammonemia type II
(OTC deficiency)

x linked partially dominant

Question 17

MOST SEVERE

Answer 17

Carbamoyl Phosphate Synthetase I Deficiency

Question 18

2nd MC

Answer 18

Arginosuccinate synthetase

Question 19

Essential AA that provides ORNITHINE

Answer 19

ARGININE

Question 20

Seen in adults with compromised liver function

d.t. cirrhosis, portal blood is shunted directly to the systemic circulation w/o passing through the liver

Answer 20

Acquired Hyperammonemia