Biochemistry of bile pigments and transformation Flashcards
What does bile consist of?
Bicarbonate
cholesterol, phospholipids
BILE SALTS
BILE PIGMENTS
How is haem broken down into bilirubin?
Haem is broken down into iron and a porphyrin ring
Haem is converted into biliverdin by haem oxygenase
Iron is released from the haem group and can be recycled
Biliverdin is then converted into UNconjugated bilirubin by biliverdin reductase
What is necessary for unconjugated bilirubin to be transported from the reticuloendothelial system to the liver?
Unconjugated bilirubin needs to be bound to albumin as it is a water insoluble bile pigment
What transports unconjugated bilirubin (bound to albumin) into the hepatocytes?
sinusoidal bilirubin transporter hepatocyte membranes
What enzyme is responsible for the conjugation of unconjugated bilirubin?
UDP-glucuronyl transferase
What enzyme is responsible the the conversion back into unconjugated bilirubin?
beta-glucuronidase
What pigments are produced from bilirubin by action of intestinal microflora?
Stercobilinogen into stercobilin - excreted in faeces
Stercobilinogen can be reabsorbed and taken back to liver via portal vein and is recirculated in bile
Mesobilinogen into mesobilin
Urobilinogen carried via portal vein back to liver for conjugation to be excreted by kidneys in urine as urobilin (urobilinogen oxidised into urobilin)
