Taxik

Hello, everyone! Could you please answer on some questions. I want to know about a bilirubin-albumin bond and penetration of blood brain barrier(BBB) of the healthy adult(not infant). I have some questions: 1) I read that unconjugated bilirubin is bound with albumin don't penetrate in tissue. Then why does human become yellow with elevated levels of bilirubin(eg 5 mg/dL, albumin can bind 20-25 mg/dL) and normal level of albumin? 2) In the books written that unconjugated bilirubin even with severe and long-standing jaundice can't penetrate the adult brain. Then why human who has >2-3 mg/dL of bilirubin feels neurological symptoms? 3) Can unbound unconjugated bilirubin(without albumin bond) penetrate in the adult brain? If it can, why and when? And what level is it? (P.S. I read that the BBB is impenetrable for molecules with molar mass over 500, bilirubin has 584 molar mass. Also that the bilirubin level about 60 mg/dL caused no apparent disruption in brain energy metabolism)