Final answer:
Conjugated bilirubin is predominantly seen in the serum during biliary obstruction, where bile flow is impeded, preventing its normal excretion and causing it to build up in the bloodstream.
Step-by-step explanation:
The disease state in which conjugated bilirubin is a major serum component is biliary obstruction. In cases of biliary obstruction, the flow of bile through the bile ducts is impeded. This causes conjugated bilirubin, which is normally excreted via the bile, to accumulate in the blood, leading to jaundice.
Conjugated bilirubin is a product of the normal breakdown of red blood cells. However, it is the liver's function to remove bilirubin from the blood and excrete it through bile. When the flow of bile is blocked, as in biliary tree obstruction, conjugated bilirubin cannot be excreted properly and hence builds up in the bloodstream, leading to a form of jaundice known as choluric jaundice.
On the contrary, in conditions such as hemolysis, neonatal jaundice, and erythroblastosis fetalis, unconjugated bilirubin, not conjugated bilirubin, typically accumulates due to different mechanisms including an overproduction or a lack of liver maturation sufficient to process bilirubin, respectively.