Final answer:
Conjugated bilirubin predominates in hepatocellular disease and obstruction, due to impaired processing by the liver and blockages in the bile ducts that prevent normal excretion.
Step-by-step explanation:
In hepatocellular disease and obstruction, the type of bilirubin that predominates is conjugated bilirubin. In conditions such as hepatocellular disease, the liver's ability to process bilirubin is impaired due to damaged parenchymatous cells, leading to raised levels of both conjugated and unconjugated bilirubin. Obstruction of the biliary tree, on the other hand, leads to a specific increase in conjugated bilirubin because the blockage in the bile ducts prevents it from being excreted normally, causing it to regurgitate into the hepatic veins and subsequently appear in the blood and urine, leading to jaundice.
Diseases such as Crigler-Najjar syndrome, Gilbert's disease, and chronic idiopathic jaundice all play roles in affecting the metabolism and excretion of bilirubin. However, the type of bilirubin affected depends on the condition and its effects on bilirubin uptake, conjugation, or excretion.