011 Heme Synthesis and Degradation

Question 1

where the three phases of the biosynthesis of heme occur

Answer 1

1. mitochondria
2. cytosol
3. mitochondria

Question 2

phase 1 of heme

Answer 2

mitochondrial synthesis of delta aminolevulinic acid from glycine (Gly) and succinyl coenzyme A (succinyl CoA)

Question 3

phase 2 of heme

Answer 3

cytosolic reactions involving the condensation of two deltas-alas leading to porphobilinogen and then use of four porphobilinogens to assemble the tetrapyrrole ring system of the coproporphyrinogen III

Question 4

phase 3 of heme

Answer 4

two oxidation reactions of coproporphyrinogen III to install the side chain vinyl groups in protoporphyrinogen IX and introduce the fully conjugated ring system of protoporphyrin IX, again in the mitochondria.
installation of the ferrous ion Fe2+ by ferrochelatase gives heme