A pharmaceutical company develops two antibiotics, X and Y,
that inhibit the same essential bacterial enzyme involved in cell wall
metabolism. In biochemical assays, both compounds bind the enzyme with similar
affinity. However, clinical testing reveals that Antibiotic X is effective
against both Gram‑positive and Gram‑negative infections, while
Antibiotic Y is effective only against Gram‑positive bacteria.

Considering known structural differences between Gram‑positive
and Gram‑negative bacteria, which inference best explains the
observed difference in antibacterial spectrum?

Question

A pharmaceutical company develops two antibiotics, X and Y,
that inhibit the same essential bacterial enzyme involved in cell wall
metabolism. In biochemical assays, both compounds bind the enzyme with similar
affinity. However, clinical testing reveals that Antibiotic X is effective
against both Gram‑positive and Gram‑negative infections, while
Antibiotic Y is effective only against Gram‑positive bacteria.

Considering known structural differences between Gram‑positive
and Gram‑negative bacteria, which inference best explains the
observed difference in antibacterial spectrum?

Accepted Answer

Antibiotic
Y cannot effectively cross the outer membrane of Gram‑negative bacteria

Answer

Antibiotic
X binds the target enzyme more tightly in vivo

Answer

The
target enzyme is absent in Gram‑negative bacteria

Answer

Antibiotic
Y suppresses bacterial growth rather than killing cells directly

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