The liver performs many essential metabolic functions, including carbohydrate, fat, and protein metabolism as well as hormone metabolism. The liver contains approximately 300 billion cells, mainly hepatocytes, which are central to the body's intermediary metabolism. Liver function tests evaluate proteins, enzymes, and bilirubin to assess liver health. Bilirubin is produced from the breakdown of heme in red blood cells and is transported to the liver, where it is conjugated and excreted in bile or urine. Unconjugated bilirubin becomes conjugated in the liver with glucuronic acid to increase its water solubility and allow excretion.

1. Liver Function ( Theory 1)
Second Course
Prepared by Heevi Ameen Rajab
Lecturer in clinical chemistry

2. There are approximately
300 billion cells in the liver
(80% of them are
hepatocytes)
The hepatocytes are central
to the intermediary
metabolism of the body

3. • Liver Functions:
1) Carbohydrate metabolism.
2) Fat metabolism.
3) Protein metabolism.
4) Hormone metabolism.
5) Drugs &foreign compounds; metabolism& excretion of drugs.
6) Liver is a good part in storage.
7) Also liver plays a good part in metabolism & secretion of
Bilirubin.

5. LFTs are classified as:
A- Liver protein test:
1- Albumin levels.
1- Globulin levels.
3- Albumin to globulin ratio.
4- Prothrombin time.
B- Liver enzyme test:
1- Alkaline phosphatase (ALP)
2- Alanine aminotransferase
(ALT)
3- Aspartate aminotransferase
(AST)
4- g-glutamyl transferase (GGT)
C- Bilirubin tests:
1- Serum bilirubin.
2- Urobilinogen

6. BILIRUBIN:
Bilirubin is the water insoluble breakdown product of
normal heme catabolism.
 It’s a yellow pigment present in bile ( a fluid made by
the liver) , urine and feces .
Heme is found in hemoglobin, a principal component
of RBCs [Heme: iron + organic compound
“porphyrin”].

7. Heme four pyrrols rings connected together to form
(porphyrin).
Bilirubin consists of open chain of four pyrrols-like rings

8. Bilirubin Metabolism

9. BLOOD
CELLS
LIVER
Bilirubin diglucuronide
(water-soluble)
2 UDP-glucuronic acid
via bile duct to intestines
Stercobilin
excreted in feces
Urobilinogen
formed by bacteria KIDNEY
Urobilin
excreted in urine
CO
Biliverdin IX
Heme oxygenase
O2
Bilirubin
(water-insoluble)
NADP+
NADPH
Biliverdin
reductase
Heme
Globin
Hemoglobin
reabsorbed
into blood
Bilirubin
(water-insoluble)
via blood
to the liver
INTESTINE
Catabolism of hemoglobin
unconjugated

10. Plasma Bilirubin. Summary of bilirubin metabolism:
1. Senescent red cells are major source of hemeproteins
2. Breakdown of heme to bilirubin occur in macrophage of
reticuloendothelial system (tissue macrophages, spleen and liver).
3. Unconjugated bilirubin is transported through blood (complex to
albumin) to liver.
4. Bilirubin is taken into liver and conjugate with glucuronic acid.

11. 5. Bile is secreted into intestine where glucuronic acid is removed and
the resulting bilirubin is converted to urobilinogen.
6. A portion of urobilinogen is reabsorbed into blood, where it is
converted to the yellow urobilin and excreted by kidneys.
7. Urobilinogen is oxidized by intestinal bacteria to the brown
stercobilin.

13. • Unconjugated bilirubin:
Bilirubin that are not
conjugated with
glucuronic acid, also
called hemobilirubin,
indirected bilirubin.
•Conjugated bilirubin:
Bilirubin that are
conjugated with
glucuronic acid, also
called hepatic bilirubin,
directed bilirubin.

14. • Neonates: usually bilirubin level less than or equal 8
mg/dl is normal
• whereas in the adults 2 mg/dL would look icteric

16. Q1. why unconjugated bilirubin is converted to conjugated
bilirubin ?
Because unconjugated bilirubin is normally not excreted.
Q2.Unconjugated bilirubin is converted to conjugated
bilirubin via blood to the liver by albumin, what is the
importance of albumin in this process?
- Increase the solubility of whole molecular.
- Prevent unconjugated bilirubin freely come into other tissue,
cause damage.

17. The End