This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
True regarding unconjugated bilirubuin is ? 
Select and explain. 
A. Not lipid soluble, B. More water soluble, C. Excreted by kidney easily, D. Bound with serum albumin
D: Bound with serum albumin
Answer: D: Bound with serum albumin 
Explanation: Ans. is 'd' i.e., Bound with serum albuminUnconjugated bilirubin Unconjugated bilirubin is highly lipid soluble (lipophilic).It is insoluble in water and tightly bound to albumin --> cannot be excreted in urine.o Unbound fraction, which is increased in hemolytic reactions (e.g. erythroblastosis fetalis), can cross blood brain barrier because of lipophilic nature and can cause brain damage of newborn --> Kernicterus.Conjugated bilirubin Conjugated bilirubin is water soluble and only loosely bound to albumin and thus is easily filtered by glomeruli and excreted in urine.