This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: HAEM synth and porphyrias, Subject name: Biochemistry
In first step of haem synthesis, which amino acid is required ? 
Select and explain. 
A. Histidine, B. Folate, C. Glycine, D. Fe
C: Glycine
Answer: C: Glycine 
Explanation: Synthesis of heme: In first step of Haem synthesis, Glycine amino acid is required Glycine condenses with succinyl CoA to form 6-amino levulinate which serves as a precursor for heme synthesis.. Copper is necessary for the synthesis of haemoglobin (Cu is a constituent of ALA synthase, needed for heme synthesis.) Pyridoxal phosphate is required for the synthesis of d-amino levulinic acid (the precursor for heme) Conversion of Succinyl CoA to a-Amino-b-ketoadipate requires pyridoxal phosphate. This is the first step of synthesis of heme that takes place in the mitochondria. a-Amino-b-ketoadipate is rapidly decarboxylated to d-aminolevulinate. Succinyl-CoA+glycine- a-amino-b-ketoadipate+CoA-SH-d-aminolevulinate+CO2