## Core Concept
Tetracycline is a broad-spectrum antibiotic that inhibits protein synthesis by binding to the bacterial 30S ribosomal subunit. This action prevents the attachment of aminoacyl-tRNA to the ribosomal complex, thereby inhibiting bacterial growth. Tetracyclines are effective against a wide range of bacteria, including both Gram-positive and Gram-negative bacteria.

## Why the Correct Answer is Right
The correct mechanism of action of tetracycline involves its binding to the 30S subunit of the bacterial ribosome. This binding interferes with the initiation complex of peptide formation, which is essential for protein synthesis. As a result, tetracycline effectively inhibits the growth of bacteria by preventing them from producing vital proteins.

## Why Each Wrong Option is Incorrect
* **Option A:** This option is incorrect because tetracycline does not act by inhibiting cell wall synthesis; that mechanism is characteristic of beta-lactam antibiotics like penicillins and cephalosporins.
* **Option B:** This option is incorrect because tetracycline does not primarily act by disrupting cell membranes; that is the mechanism of antifungal agents like polyenes (e.g., amphotericin B) and some antiseptics.
* **Option C:** This option might seem plausible because some antibiotics do inhibit protein synthesis by binding to the 50S ribosomal subunit (e.g., macrolides like erythromycin). However, tetracycline is specific to the 30S subunit.

## Clinical Pearl / High-Yield Fact
A key point to remember about tetracyclines, including tetracycline, is that they are contraindicated in children under 8 years of age and in pregnant women due to the risk of inhibiting bone growth and causing tooth discoloration. This is a critical consideration in clinical practice.

## Correct Answer Line
**Correct Answer: D.**