Orange-yellow pigment in bile formed by breakdown of hemoglobin

• A. Albumin test
• B. Amniocentesis
• C. Bilirubin
• D. Angiography

Answer: (C)

Bilirubin is the orange-yellow pigment formed when heme from broken-down hemoglobin is processed. Old red blood cells are taken up by macrophages, heme is converted to biliverdin and then to bilirubin, which is carried in the blood bound to albumin to the liver. In the liver, bilirubin is conjugated with glucuronic acid and excreted into bile. This bilirubin in bile gives the characteristic yellowish color. If bile flow or bilirubin processing is impaired, that pigment can accumulate and contribute to jaundice.

The other options don’t describe this pigment: a test for albumin measures a blood protein, not bile pigment; amniocentesis is a prenatal fluid sampling procedure; angiography images blood vessels using contrast.