Drive - bilirubin and haemoglobin Flashcards
What are bile pigments formed from?
The haem portion of broken down erythrocytes
Where are old/damaged erythrocytes broken down?
The spleen, bone marrow and liver
Describe the role of hemoxygenase (enzyme):
To breakdown the haem group into biliverdin, Fe2+ and CO
Describe the role of biliverdin reductase:
Reduce biliverdin to the unconjugated
Name 2 key properties of unconjugated bilirubin:
Toxic
Lipid soluble (therefore insoluble in the blood)
How is unconjugated bilirubin converted to conjugated bilirubin?
In glucuronidation under the action of the enzyme UDP Glucuronyl Transferase
What form of bilirubin can be found in bile?
Conjugated bilirubin
What does reduction (hydrolysis) by intestinal bacteria cause the conversion of?
Conjugated bilirubin to be converted into urobilinogen
What % of urobilinogen is reabsorbed into the blood?
10%
What happens to the urobilinogen that is reabsorbed back into the blood?
Bound to albumin and transported to the liver where it is oxidised to urobilin
What happens to urobilin?
Either re-cycled into bile or excreted in urine
What does urobilin in urine do?
Gives urine its yellowish colour
What happens to the 90% of urobilinogen that is not reabsorbed into the blood
It is oxidised by different intestinal bacteria to form stercobilin
What happens to stercobilin?
It is excreted in faeces (responsible for the brownish colour)
What cause jaundice?
High serum bilirubin levels.
What are the 3 main types of jaundice?
Pre-hepatic
Hepatic
Post-hepatic
What key levels are raised in pre-hepatic jaundice?
Increased serum unconjugated bilirubin
Without excess bilirubin in the urine
What causes pre-hepatic jaundice (general)?
Increased breakdown of erythrocytes
What causes hepatic jaundice (general)?
The cells of the liver are damaged so unable to metabolise the unconjugated bilirubin
What key levels are raised in hepatic jaundice?
Increased serum unconjugated bilirubin
AND
Increased serum conjugated bilirubin
What causes post-hepatic jaundice (general)?
When the biliary system is damaged, inflamed or obstructed
What key levels are raised in post-hepatic jaundice?
Increased serum conjugated bilirubin
What is a gall stone made from and how does it form?
Made from cholesterol.
Formed when cholesterol levels become high, the cholesterol will crystallise out of the solution (and form a gall stone)
