Which two fractions are included in conjugated bilirubin?

Conjugated bilirubin consists primarily of bilirubin that has been processed in the liver and is water-soluble. The two key fractions included in conjugated bilirubin are monoglucuronide and diglucuronide. These forms result from the glucuronidation process, where the enzyme UDP-glucuronosyltransferase adds glucuronic acid to bilirubin, making it soluble and thereby facilitating its excretion in bile and urine.

Monoglucuronide represents bilirubin that has had one glucuronic acid molecule attached. In contrast, diglucuronide has two glucuronic acid molecules. This process is essential for the body to eliminate bilirubin, especially when produced from the breakdown of hemoglobin, as unconjugated bilirubin is not water-soluble and cannot be excreted effectively.

The other options do not provide components relevant to conjugated bilirubin. Free bilirubin refers to the unconjugated form of bilirubin and does not relate to the conjugated fraction. Haptoglobin and hemoglobin are involved in the transport and metabolism of free hemoglobin, not bilirubin. Transferrin and ferroportin are related to iron metabolism and not directly to bilirubin processing. Hence, the focus on