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
Which of the following enzyme of Heme synthesis is located in mitochondria? 
Select and explain. 
A. ALA synthase, B. ALA dehydratase, C. Uroporphyrinogen I synthase, D. Uroporphyrinogen decarboxylase
A: ALA synthase
Answer: A: ALA synthase 
Explanation: First reaction and the last 3 reactions of heme synthesis take place in the mitochondria. The rest of them takes place in cytosol. Figure: Heme synthesis occuring in mitochondrion & cytosol