Explain the metabolic relationship between haemoglobin synthesis and folic acid

•   Folic acid is itself not biologically active until it has been converted into tetrahydrofolate via the enzyme dihydrofolate reductase in the liver. Therefore, folic acid is a precursor of tetrahydrofolate.

•   In order to biosynthesize glycine, the amino acid serine is required, where the enzyme serine hydroxymethyltransferase catalyses the reaction between serine and tetrahydrofolate into glycine.

•   The committed step for porphyrin biosynthesis (the prosthetic group that contains an iron atom contained in the center of a large heterocyclic organic ring) is the formation of D-aminolevulinic acid by the reaction of the amino acid glycine and succinyl-CoA, from the citric acid cycle. Therefore, glycine is a precursor of porphyrin.
[1] Folic Acid Tetrahydrofolate
[2] Tetrahydrofolate Glycine
[3] Glycine Porphyrin

•   In all, a lack of folic acid impairs hemoglobin synthesis.