Final answer:
Sulfonamides are antimicrobial agents that act as structural analogues of PABA, serving as antimetabolic drugs and indirectly inhibiting nucleic acid synthesis in bacteria.
Step-by-step explanation:
Sulfonamides, often referred to as sulfa drugs, are a group of synthetic antibiotics that contain the sulfonamide group. These drugs are structural analogues of para-aminobenzoic acid (PABA), acting as antimetabolic agents because they competitively inhibit the enzyme in the bacterial folic acid synthesis pathway. As a result, they indirectly inhibit the synthesis of nucleic acids necessary for bacterial growth by obstructing the production of dihydrofolic acid, a precursor to folic acid and subsequently, to purines and pyrimidines needed for nucleic acid synthesis.
Humans, unlike bacteria, do not synthesize folic acid and obtain it from their diet, making sulfonamides selectively toxic to bacteria. The response to the question 'Are sulfonamides structural analogues of PABA, antimetabolic drugs, and do they indirectly inhibit the synthesis of nucleic acids?' is E) A, B, and C, because sulfonamides are indeed structural analogues of PABA (A), function as antimetabolic drugs (B), and by their mechanism of action, indirectly inhibit nucleic acid synthesis (C).