Final answer:
Bacteria resistant to sulfonamides have enzymes with a greater affinity for PABA (para-aminobenzoic acid), allowing them to continue synthesizing folic acid even in the presence of the drug.
Step-by-step explanation:
The bacteria that are resistant to sulfonamide have enzymes that show a greater affinity for PABA (para-aminobenzoic acid) rather than sulfonamide. Sulfonamides work by inhibiting the bacterial enzyme dihydropteroate synthase, which is involved in the synthesis of folic acid. The binding site of this enzyme typically binds to PABA, where it takes part in a crucial step in folic acid synthesis. However, in the presence of sulfonamide, the drug competes with PABA for the active site of the enzyme, potentially inhibiting the synthesis of folic acid and thus halting bacterial reproduction. If bacteria are sulfonamide-resistant, it suggests their dihydropteroate synthase has a greater affinity for PABA, allowing them to continue synthesizing folic acid even in the presence of the drug.
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