Bilirubin is transported from reticuloendothelial cells to the liver by which protein?

Bilirubin is a breakdown product of hemoglobin derived from the degradation of red blood cells. Once formed in the reticuloendothelial system, it is transported to the liver for further processing, mainly for conjugation and subsequent excretion into bile. The transport of bilirubin in the bloodstream is primarily facilitated by albumin.

Albumin is a major plasma protein that has a high affinitive binding capability for unbound (free) bilirubin, which is hydrophobic and would otherwise be poorly soluble in plasma. By binding to albumin, bilirubin is rendered more water-soluble, allowing it to be transported effectively to the liver. The binding of bilirubin to albumin protects it from being cleared by the kidneys and facilitates its delivery to the liver, where it can be conjugated with glucuronic acid to increase its solubility and promote excretion.

Other proteins mentioned in the options have distinct roles in the body. Globulins are a group of proteins that include antibodies but do not function in bilirubin transport. Transferrin is primarily responsible for iron transport in the bloodstream, while haptoglobin binds free hemoglobin to prevent iron loss and renal damage in hemolysis; neither of these plays a significant role in