Which of the following inhibits protein synthesis by binding to 50 S ribosome

Options

A. Tetracycline
B. Streptomycin
C. Erythromycin
D. Penicillin.

Answer

To solve the question "Which of the following inhibits protein synthesis by binding to the 50 S ribosome?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for an antibiotic that inhibits protein synthesis specifically by binding to the 50 S ribosomal subunit.

2. **Identify the Options**: The options provided are:
- Option 1: Tetracycline
- Option 2: Streptomycin
- Option 3: Erythromycin
- Option 4: Penicillin

3. **Review Antibiotic Mechanisms**:
- **Tetracycline**: This antibiotic binds to the 30 S ribosomal subunit, inhibiting protein synthesis.
- **Streptomycin**: This antibiotic also binds to the 30 S ribosomal subunit, inhibiting protein synthesis.
- **Erythromycin**: This antibiotic binds to the 50 S ribosomal subunit, inhibiting protein synthesis.
- **Penicillin**: This antibiotic works by inhibiting cell wall synthesis and does not directly affect protein synthesis.

4. **Determine the Correct Answer**: Based on the mechanisms of action:
- Tetracycline and Streptomycin bind to the 30 S subunit and are not correct.
- Erythromycin binds to the 50 S subunit and is the correct answer.
- Penicillin does not inhibit protein synthesis.

5. **Conclusion**: The antibiotic that inhibits protein synthesis by binding to the 50 S ribosome is **Erythromycin** (Option 3).

### Final Answer:
**Erythromycin (Option 3)** is the correct answer.

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