Plasma bilirubin
A. Is a steroid pigment.
B. Is converted to biliverdin in the liver.
C. Does not normally cross cerebral capillary walls.
D. Is freely filtered in the renal glomerulus.
E. Is sensitive to light.
The correct answers are C. Does not normally cross cerebral capillary walls and E. Is sensitive to light.
Plasma bilirubin is a yellow-orange pigment produced during the breakdown of hemoglobin in red blood cells. Here’s why the other options are incorrect:
A. Bilirubin is a tetrapyrrole pigment, not a steroid pigment.
B. Bilirubin is converted from biliverdin in the liver, not the other way around. Biliverdin is reduced to bilirubin by the enzyme biliverdin reductase.
D. Bilirubin is not freely filtered in the renal glomerulus because it’s bound to albumin, making it too large to pass through the glomerular filtration barrier.