The step blocked by sulfonamides and PAS is which step?

Unlock all questions

This demo includes only 20 questions. Upgrade to access hundreds of questions, flashcards, exam simulations, and disable ads.

Full question bankExam simulationsFlashcards
From $24.99Unlock all

Prepare for the Drug Action 2 Exam. Focus on multiple-choice questions, learn through interactive quizzes, and understand core drug mechanisms with explanations. Dive deep into pharmacokinetics and pharmacodynamics to ace your test!

Multiple Choice

The step blocked by sulfonamides and PAS is which step?

Explanation:
Sulfonamides and PAS block the initial step of bacterial folate synthesis. They act as PABA mimics and competitively inhibit dihydropteroate synthase, the enzyme that combines PABA with the pteridine precursor to form dihydropteroate. Because this is the first step in making dihydrofolate and ultimately tetrahydrofolate, blocking it prevents the downstream production of essential one-carbon units needed for thymidine (DNA) synthesis. This is why these drugs are effective: bacteria must synthesize folate de novo, whereas humans obtain folate from their diet. The later step, reduction of dihydrofolate to tetrahydrofolate, is blocked by another drug (trimethoprim), not by sulfonamides or PAS.

Sulfonamides and PAS block the initial step of bacterial folate synthesis. They act as PABA mimics and competitively inhibit dihydropteroate synthase, the enzyme that combines PABA with the pteridine precursor to form dihydropteroate. Because this is the first step in making dihydrofolate and ultimately tetrahydrofolate, blocking it prevents the downstream production of essential one-carbon units needed for thymidine (DNA) synthesis. This is why these drugs are effective: bacteria must synthesize folate de novo, whereas humans obtain folate from their diet. The later step, reduction of dihydrofolate to tetrahydrofolate, is blocked by another drug (trimethoprim), not by sulfonamides or PAS.

More Multiple Choice Questions
Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy