Which protein serves as a transport protein for bilirubin in the blood?

Which protein serves as a transport protein for bilirubin in the blood?

• A. Albumin
• B. Alpha1-globulin
• C. Beta-globulin
• D. Gamma-globulin

Answer: (A)

Bilirubin is hydrophobic and cannot travel in blood on its own, so it needs a carrier. Albumin serves as the primary transport protein for unconjugated bilirubin in the bloodstream. It binds bilirubin tightly but reversibly, forming a soluble complex that safely escorts it to the liver, where bilirubin is conjugated to become water-soluble for excretion into bile. The other plasma protein fractions—alpha1-globulins, beta-globulins, and gamma-globulins—have different roles (enzymes, various transporters, antibodies) and do not primarily transport bilirubin.

Bilirubin is hydrophobic and cannot travel in blood on its own, so it needs a carrier. Albumin serves as the primary transport protein for unconjugated bilirubin in the bloodstream. It binds bilirubin tightly but reversibly, forming a soluble complex that safely escorts it to the liver, where bilirubin is conjugated to become water-soluble for excretion into bile. The other plasma protein fractions—alpha1-globulins, beta-globulins, and gamma-globulins—have different roles (enzymes, various transporters, antibodies) and do not primarily transport bilirubin.