Approximately what proportion of total body heme synthesis occurs in the erythroid cells of the bone marrow?

• A About 25 percent
• B About 50 percent
• C About 85 percent ✓
• D About 99 percent

Explanation

Roughly 85 percent of daily heme synthesis occurs in developing erythroid cells for hemoglobin production; the liver accounts for most of the remainder, synthesising heme mainly for cytochrome P450 enzymes. Because the liver cannot store heme, it must continually regulate ALAS1 according to demand, whereas erythroid cells rely on ALAS2 regulated primarily by iron availability via IRP control of translation.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.