Bilirubin formation Flashcards
Time when RBC are phagocytized in Reticuloendothelial System
Approximately 126 days
Degradation product of hemoglobin
Globin (recycled in liver) and heme
Action of heme after release of iron
Binds with transferrin to be transported to liver
Heme conversion through Heme Oxygenase
Heme → biliverdin
Biliverdin conversion through Biliverdin Reductase
Biliverdin → unconjugated bilirubin (B1)
Transport form of unconjugated bilirubin (B1) in plasma
B1 binds with albumin
Action of albumin in hepatocytes
Albumin detaches on the surface of hepatocytes
Transport of B1 to the liver
B1 binds to ligandin to enter the SER
Conjugation of B1 in the liver
B1 undergoes esterification and conjugation
Enzyme catalyzing B1 conjugation
Uridine Diphosphate Glucuronyl Transferase (UDPGT)
Conversion of B1 to B2
UDPGT converts B1 to Bilirubin diglucuronide (B2)
Action of UDPGT
Promotes transfer of glucuronyl/glucuronide to each of bilirubin’s two propionic side chains
Excretion of B2 from hepatocytes
B2 is excreted through bile canaliculi
Storage of B2 in the liver
B2 is transported to the gall bladder for storage
Action of bile during meals
Bile emulsifies fats in the small intestine
Conversion of B2 in the large intestine
Normal flora acts on B2 → mesobilirubin
Further reduction of mesobilirubin
Mesobilirubin → mesobilirubinogen → urobilinogen (colorless)
Fate of 80% of urobilinogen
Oxidized to urobilin/stercobilin (yellow-brown stool pigment)
Fate of 20% of urobilinogen
Reabsorbed, recycled through liver, and reexcreted
Fate of small amount of 20% urobilinogen
Filtered by kidneys and excreted in urine
Effect of bilirubin metabolism problems
Changes in urine and stool appearance
Plasma B2 increase effect
Evident changes in urine
