What is the Difference Between Conjugated and Unconjugated Bilirubin?

The difference between conjugated and unconjugated bilirubin lies in their solubility, binding properties, and roles in the body. Bilirubin is a yellow-colored pigment and a metabolite of heme, formed when the haemoglobin of red blood cells undergoes breakdown.

Unconjugated bilirubin, also known as indirect bilirubin, is insoluble in water and requires the protein carrier (albumin) to move in the bloodstream. It is unable to be conjugated by the liver and re-enters enterohepatic circulation. Unconjugated bilirubin is measured by subtracting the direct-reacting fraction from total bilirubin.

Conjugated bilirubin, also known as direct bilirubin, is soluble in water and does not require albumin to travel in the bloodstream. It is processed by the liver and is ready to be excreted through stool and urine. Conjugated bilirubin is formed when glucuronic acid is added to unconjugated bilirubin by the enzyme glucuronyl transferase.

In summary, the main differences between conjugated and unconjugated bilirubin are:

• Solubility: Unconjugated bilirubin is insoluble in water, while conjugated bilirubin is soluble in water.
• Binding: Unconjugated bilirubin requires albumin to move in the bloodstream, whereas conjugated bilirubin does not.
• Liver processing: Unconjugated bilirubin is unable to be conjugated by the liver, while conjugated bilirubin is processed by the liver for excretion.

Comparative Table: Conjugated vs Unconjugated Bilirubin

Here is a table comparing the differences between conjugated and unconjugated bilirubin:

Both conjugated and unconjugated bilirubin are produced when red blood cells break down, and both are types of bilirubin that are metabolized in the liver. However, conjugated bilirubin is water-soluble and can be excreted by the body, while unconjugated bilirubin is not water-soluble and cannot be excreted without being converted into a water-soluble form.