Which of the following is true about Penicillin G?
**Core Concept**
Penicillin G is a narrow-spectrum beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs) on the bacterial cell wall. It is effective against Gram-positive and some Gram-negative bacteria.
**Why the Correct Answer is Right**
Penicillin G exerts its bactericidal effect by inhibiting the transpeptidation reaction, which is essential for the cross-linking of peptidoglycan layers in the bacterial cell wall. This results in weakened cell walls and ultimately leads to cell lysis and death. Penicillin G is specifically targeted to PBPs on the bacterial cell wall, which are responsible for the cross-linking of peptidoglycan chains.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Penicillin G is not a broad-spectrum antibiotic. It is primarily effective against Gram-positive bacteria and some Gram-negative bacteria.
**Option B:** This option is incorrect because Penicillin G does not act by inhibiting protein synthesis. It targets the bacterial cell wall, not the ribosomes.
**Option C:** This option is incorrect because Penicillin G is not metabolized by the liver. It is primarily excreted unchanged in the urine.
**Clinical Pearl / High-Yield Fact**
Penicillin G is a time-dependent antibiotic, meaning that its effectiveness is dependent on maintaining a sufficient concentration above the minimum inhibitory concentration (MIC) for a prolonged period of time. This requires dosing every 4-6 hours to maintain therapeutic levels.
**Correct Answer:** C.