Biochem- Heme Synthesis

Question 1

State the rate limiting step of Heme Synthesis.

Answer 1

Reaction — Glycine + Succinyl CoA = d- ALA (aminolevulinic acid)
Enzyme: D- ALA Synthase.

Note: Takes place in the mitochondria then transferred to the cytosol.

Question 2

State the necessary factor for the 1st reaction of heme synthesis.

Answer 2

B6- Pyridoxal phosphate.

Question 3

Describe the Synthesis of Heme.

Answer 3

Clue: Get Some Additional Points Having Understood the Correct Proper Pathway for Heme.

Question 4

State the metabolism of bilirubin

Answer 4

1. Bilirubin is conjugated with glucoronic acid.
2. Enzyme involved - UDP- glucuronyltransferase
3. Conjugated bilirubin is secreted into the bile duct
4. Coverted into urobilinogen by bacteria in the gut
5. Oxidized to stercobilin
6. Excreted in feces via large intestine and urine via kidney.

Question 5

State the causes of bilirubin

Answer 5

1. Physical blockage
2. Liver disease
3. Haemolytic anemia
4. Decreased bilirubin conjugation

Question 6

Describe Prehepatic Jaundice.

Answer 6

Disruption of pathway before the liver.
Caused by a excess production of bilirubin
Abnormality with RBCs
High plasma concentration of unconjugated bilirubin

Question 7

Describe Intra-hepatic Jaundice

Answer 7

1. Disruption of pathway within liver.
2. Caused by a generalized liver dysfunction.
   (Caused by infection, physical and alcohol damage)
3. Impaired uptake, conjugation and secretion of bilirubin.

Question 8

Describe Posthepatic Jaundice

Answer 8

1. Disruption of pathway beyond the liver.
2. Caused by blockage of bile duct.
3. Plasma bilirubin is conjugated and bile salts is accumulated in plasma
4. Characterized by pale stools and dark colored urine