Bilirubin & Haem Catabolism Flashcards
What are bile pigments formed from?
The haem portion of haemoglobin when old/damaged erythrocytes are broken down
Where are RBC broken down?
Spleen and liver
What is the predominant bile pigment?
Where is it extracted from?
Bilirubin
From the blood by hepatocytes and actively secreted into bile
What colour is bilirubin & what does it contribute to?
Yellow
To the colour of bile
When erythrocytes are old and damaged what are they broken down by and where?
Macrophages (are phagocytic)
Spleen and bone marrow
But can also occur in the kupffer cells (resident macrophages) of liver
Hb is broken down into what and by what?
Into haem and globin by splenic macrophages
What happens to globin?
Where does it go?
Globin is broken down into AA, used to generate new erythrocytes in the bone marrow
Haem—->?
Emzymes?
Broken down to biliverdin, CO and Fe2+
Hemoxygenase
What happens to Fe2+, where does it go?
It is bound to iron transporter, transferrin, shuttled to bone marrow to be used in new erythrocytes
Biliverdin —-> ?
Enzyme?
Unconjugated bilirubin
Biliverdin reductase
What is unconjugated bilirubin?
Toxic
Lipid soluble and insoluble in blood
What will happen to unconj bilirubin?
Where does it go and what happens to it?
It is bound to albumin, transported to liver
Glucuronidation takes place (add a glucuronic acid to make it more soluble)
Unconj bilirubin —-> ?
Enzyme?
Conjugated bilirubin
UDP glucuronyl transferase
Where does conj bilirubin go?
It is dissolved in bile, enters the duodenum
Where does the conj bilirubin travel to?
Ileum, beginning of large intestine
What happens to the conj bilirubin in the intestine?
What does it form?
Intestinal bacteria reduce it thru hydrolysis
Forms urobillinogen
Urobillinogen is …..
Lipid soluble
What 2 things happen and % to urobillinogen?
10% reabsorbed by blood
90% oxidized by bacteria
What happens to the 10% of urobillinogen?
It is reabsorbed by blood, bound to albumin, transported back to the liver and oxidized to urobilin
Either recycled In bile or goes to kidney as urine
What happens to 90% of urobillinogen?
Oxidized by diff type of intestinal bacteria to form stercobilin, excreted in stool
