22: Nitrogen Metabolism

Question 1

Three sources of protein for the AA pool

Answer 1

Dietary, body protein, synthesis of non-essential AAs

Question 2

Final step to nitrogen removal of an AA?

Answer 2

Oxidative deamination

Question 3

Inheritance for cystinuria and hartnup disease

Answer 3

Autosomal recessive

Question 4

Lack of which two things in the body cause specific symtpoms of Hartnup disease?

Answer 4

Lack of NAD/NADP -> neuro defects

Lack of serotonin and melatonin -> mood sx

Question 5

Most common IEM and the first to be included in newborn screenings

Answer 5

PKU

Question 6

What enzyme forms THB (BH4)?

Answer 6

Dihydrobiopterin reductase

Question 7

What does THB do?

Answer 7

Essential cofactor in hydroxylation of aromatic AAs

Question 8

Defects in THB lead to what?

Answer 8

Secondary PKU

Question 9

Initiating step of the urea cycle

Answer 9

NAG synthase forming NAG

Question 10

What is carbamoyl phosphate synthetase II involved in?

Answer 10

First step of de novo pyrimidine synthesis

Question 11

Defects in urea cycle enzymes: all are autosomal recessive except which? What disorder does it cause?

Answer 11

Ornithine transcarbamoylase -> X linked, orotic aciduria

Question 12

CPSase I vs CPSase II: location, process, and what activates it

Answer 12

CPSase I: mito, urea cycle, NAG-activated

CPSase II: cytosol, pyrimidine synthesis, PRPP activated

Question 13

Which type of bilirubin is insoluble?

Answer 13

Unconjugated bilirubin is insoluble

Question 14

What agents causes insoluble bilirubin to become more soluble?

Answer 14

Diazo reagent

Question 15

What removes bilirubin from blood in the fetus vs after birth?

Answer 15

Placenta vs liver