Question:easy
Sulphonamide injection causes decrease in folic acid by?
Sulphonamide injection causes decrease in folic acid by?
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The drug mimics PABA and fights for the same enzyme site.
Updated On: Jun 24, 2026
- Competitive inhibition
- Non competitive inhibition
- Uncompetitive inhibition
- Allosteric inhibition
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The Correct Option is A
Solution and Explanation
Step 1: Folate is essential for bacterial DNA synthesis, and bacteria build it from scratch using PABA as a precursor with the help of dihydropteroate synthase.
Step 2: Sulphonamides mimic the shape of PABA so closely that the enzyme accepts the drug instead of the true substrate, stalling folate production and starving the cell of nucleotide precursors.
Step 3: The defining feature here is that the drug and PABA fight for the very same binding pocket. Raising PABA levels displaces the drug, restoring enzyme activity, which is exactly what competitive antagonism predicts.
Step 4: The other options describe inhibitors acting away from the substrate site or irreversibly, none of which fit a substrate look-alike. So the mechanism is competitive.
\[\boxed{\text{Competitive inhibition}}\]
Step 2: Sulphonamides mimic the shape of PABA so closely that the enzyme accepts the drug instead of the true substrate, stalling folate production and starving the cell of nucleotide precursors.
Step 3: The defining feature here is that the drug and PABA fight for the very same binding pocket. Raising PABA levels displaces the drug, restoring enzyme activity, which is exactly what competitive antagonism predicts.
Step 4: The other options describe inhibitors acting away from the substrate site or irreversibly, none of which fit a substrate look-alike. So the mechanism is competitive.
\[\boxed{\text{Competitive inhibition}}\]
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