Multiple choice The biosynthesis of heme requires all of the following except propionic acid succinyl CoA glycine ferrous ion Reveal answer Fill a bubble to check yourself A Correct answer Explanation Heme biosynthesis requires succinyl CoA, glycine, and ferrous ion as key substrates. Propionic acid is not involved in heme synthesis - it's a fatty acid that can be converted to succinyl CoA via propionyl CoA, but is not a direct reactant.