In heme synthesis in mammalian cells:

1. Succinyl CoA and alanine are the immediate substrates for formation of d-aminolevulinic acid
2. Ferric iron is inserted into protoporphyrin IX
3. Coproporphyrin IV is an intermediate
4. Porphobilinogen is formed by the condensation of two molecules of d-aminolevulinic acid

Wrong, please choose another answer

Comments:

1.  
2. Ferrous iron, or iron (II), is inserted to make heme
3.  
4.