This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
The relationship between sulphonamide and PABA is 
Select and explain. 
A. Metabolic antagonism, B. Synergism, C. Intermediate compound formation, D. Chelation
A: Metabolic antagonism
Answer: A: Metabolic antagonism 
Explanation: Sulfonamides have structural similarity with PABA .therefore, they competitively inhibit the enzyme responsible for the incorporation of PABA into dihydropteroic acid, the immediate precursor of folic acidRef: DM Vasudevan, 7th edition, page no: 491, 61