Heme biosynthesis is inhibited in lead poisoning because lead disrupts the enzymatic activity of ALA dehydratase and ferrochelatase, which are required for heme biosynthesis. The other choices are incorrect because while the initial steps of heme biosynthesis occur in the mitochondria, the remaining steps occur in the cytosol, and large molecules can be transported across the mitochondrial membrane.

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Heme Biosynthesis

Question 38

Multiple Choice

Heme biosynthesis

A) requires that synthesis of the protoporphryin ring occur in the mitochondria due to difficulties in transporting large molecule.
B) is inhibited in lead poisoning.
C) can be completed using enzymes from the cytosol.
D) A and B
E) A,B,and C

Correct Answer: