This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2019, Subject name: Biochemistry
Which TCA intermediate is used in haem synthesis: 
Select and explain. 
A. Fumarate, B. Alpha keto gluterate, C. Malate, D. Succinyl CoA
D: Succinyl CoA
Answer: D: Succinyl CoA 
Explanation: Solutions: - The first step of haem synthesis uses succinyl CoA which is intermediate to TCA. Fumarate, Alpha keto gluterate and malate (4C) is also intermediate to TCA. Malonate (3C) or malonyl CoA is inhibitor of 3 pathways in body - Succinate DH of TCA - Complex 2 of ETC - Beta oxidation of Fatty acid Acetyl CoA is not an intermediate of TCA. Haem synthesis It occurs in Mitochondria + cytoplasm (So, doesn't occurs in RBC)