Heme Catabolism

Question 1

Sources of heme in human body

Answer 1

RBCs turnover “major”

Cytochrome, myoglobin, and CytP450 “minor”

Question 2

Steps of heme catabolism

Answer 2

1. Heme oxidation
2. Transport of bilirubin
3. Uptake by liver and conjunction
4. Excretion of conjugated bilirubin

Question 3

Oxidation of heme by……

Answer 3

Microsomal hemeoxygenase that requires NADPH and O2

Then by a NADPH dependent hydrogenase

Question 4

1st step of oxidation produces…..

Answer 4

Biliverdin

Question 5

Microsomal hemeoxygenase catalyzes the cleavage of…….

Answer 5

Methenyl bridge between 1st and 2nd pyrrole rings

Question 6

……is produced in the 1st step of oxidation

Answer 6

Biliverdin, Fe+2, CO

Question 7

Bilirubin is transported in blood by……

Answer 7

Binding to albumin by non covalent bond

Question 8

Enzyme that catalyzes conjugation

Answer 8

Glucuronyl transferase

Question 9

……..gives the stool it’s brown color

Answer 9

Stercobilin

Question 10

……gives the urine its yellow color

Answer 10

Urobilin

Question 11

Bilirubin diglucuronide is converted to bilirubin by …….

Answer 11

Bacterial glucuronidase

Question 12

Glucuronic acid is the oxidized form of glucose at …..

Answer 12

C6

Question 13

Site oh glucuronic acid pathway……

Answer 13

Cytoplasm of liver cells

Question 14

Importance of UDP glucuronic acid

Answer 14

1. Detoxification of some compounds
2. It is a component of glycosaminoglycans and proteoglycans
3. Converted to L-Xylulose then to D-Xylulose that can enter the HMP pathway