urea cycle

Question 1

what is the first step of the urea cycle? where is it happening?

substrate, products? Importance?

Answer 1

mitochondial reaction

substrates: ammonia and co2 (or bicarbonate)

2 ATP

e: carbomoyl phosphate synthetase 1
product: carbomoyl phosphate

Question 2

what is this? where does it go next?

Answer 2

carbamoyl phosphate

combines with ornithine to create citruline in the mitochondia

Question 3

what are these and what do they create?

with which enzyme?

Answer 3

they were ornithine and carbamoyl phosphate

they create citruline (see below) with ornithine trasncarbamoylase

Question 4

what are these and what do they create?

with which enzyme?

Answer 4

aspartate (asp) and citruline produce arginosuccinate (seen below) with ATP

Arginosuccinate synthetase

Question 5

what are these and what do they create?

with which enzyme?

Answer 5

arginosuccinate and fumarate leaving

this produces arginine

enzyme: Arginosuccinate lyase

Question 6

what is this and in the urea cycle, what does it produce via which enzyme?

Answer 6

arginine will meet the enzyme arginine lyase and forms ornithine and urea

Question 7

when citruline is formed, where does it go?

Answer 7

it leaves the mitochondia through a citruline transporter and enters the cytosol for the remainder if the urea cycle

Question 8

when ornithine is formed, where does it go to continue the urea cycle? how?

Answer 8

ornithine goes back into the mitochondia via ornithine transporter

Question 9

what is trypsin? where does it cut?

Answer 9

trypsin is an endopeptide that cuts the peptide bond after (on the c term side) arginine and lysine

Question 10

what is chymotrypsin? where does it cut?

Answer 10

trypsin is an endopeptide that cuts the peptide bond after (on the c term side) of aromatic amino acids

tyrosine, phenylalanine, tryptophan

Question 11

how many ATP are needed for one urea cycle?

Answer 11

4 atp per cycle

Question 12

what is the activator of carbamoyl phosphate synthetase 1?

Answer 12

N acetyl glutamate

Question 13

n acetyl glutamate is made how? what activates this reaction?

Answer 13

glutamate + acetyl-coa + atp

enzyme: n acetyl glutamate synthetase

arginine activates the production of n acetyl glutamate

Question 14

what are the 3 ways the urea cycle can be regulated?

Answer 14

1: high protein diet causes 10-20x higher enzyme levels
2: N acetyl glutamate activates the 1st step (the rate determining step)
3: high ornithine or arginine causes increased urea cycle rate