Bilirubin, heme, & homocystinuria

Question 1

What reaction is responsible for the greenish color of bruises?

Answer 1

heme to biliverdin

enzyme: heme oxygenase

Question 2

What enzyme is absent in Crigler-Najjar syndrome and low in Gilbert’s syndrome and newborns?

Answer 2

UDP-glucuronyl transferase

Question 3

What is the function of UDP-glucuronyltransferase?

Answer 3

conjugate bilirubin

Question 4

What is defective in both Rotor syndrome and Dubin-Johnson syndrome?

Answer 4

(conjugated) bilirubin glucuronide secretion from the liver

Question 5

Ferrochelatase is the last enzyme in the _______ pathway. It isinhibited by _______.

Answer 5

heme synthesis; lead

Question 6

What is the defective enzyme in porphyria cutanea, the most common porphyria? What pathway is it in?

Answer 6

uroporphyrinogen decarboxylase; heme synthesis

Question 7

What may be seen at autopsy in Gilbert’s syndrome?

Answer 7

blackened liver

Question 8

Homocysteine can be metabolized in 2 ways. Which requires B6 and which B12?

Answer 8

Meat eaters can make MEAT-thionine.

SIX-tathionine synthase requires B6.

Question 9

What is the end-product of the cystathionine pathway of homocysteine metabolism?

Answer 9

Cysteine

Question 10

What are the clinical features of homocystinuria?

Answer 10

hypercoagulability -> MI in children; mental retardation; osteoporosis; kyphosis; lens subloxation

Question 11

How does homocysteine cause damage?

Answer 11

forms disulfide bonds with cysteine residues

Question 12

What is the other cofactor necessary for conversion of homocysteine to methionine?

Answer 12

methyl-THF

Question 13

Which cells of the ovarian follicle synthesize androgens?

Answer 13

Theca interna