Sulfa drugs control bacterial infections because they

  • A. denature every bacterial protein at once
  • B. dissolve the bacterial membrane
  • C. raise the temperature inside the bacterium
  • D. resemble PABA and competitively block the bacterial enzyme that uses it

Explanation

The drug mimics para-aminobenzoic acid, a substrate bacteria need to make folic acid, so it occupies the enzyme's active site and starves the pathway. Humans obtain folate from food, which is why the drug harms bacteria selectively.

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