The final step of the heme biosynthetic pathway involves:

• A Oxidation of protoporphyrinogen IX to protoporphyrin IX
• B Decarboxylation of coproporphyrinogen III to protoporphyrinogen IX
• C Condensation of glycine with succinyl-CoA
• D Insertion of ferrous iron (Fe2+) into protoporphyrin IX ✓

Explanation

Ferrochelatase, the last mitochondrial enzyme of the pathway, inserts ferrous iron (Fe2+) into protoporphyrin IX to form heme. Option B describes coproporphyrinogen oxidase, option A describes protoporphyrinogen oxidase, and option C is the ALA synthase reaction. When iron is unavailable or ferrochelatase is inhibited, as in lead poisoning or iron deficiency, zinc substitutes for iron and zinc protoporphyrin accumulates.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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