Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Tetracycline inhibits protein synthesis in bacteria.
Reason (R): It prevents binding of aminoacyl tRNA to A-site of active ribosomal subunit.
Choose the correct answer from the options given below:

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Common translation inhibitors and their targets:
- Tetracycline: Blocks aminoacyl-tRNA binding at the A-site (30S).
- Chloramphenicol: Inhibits peptidyl transferase activity (50S).
- Erythromycin: Blocks translocation along mRNA (50S).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Many antibiotics work by targeting the bacterial translation machinery, exploiting structural differences between prokaryotic (70S) and eukaryotic (80S) ribosomes.

Step 2: Detailed Explanation:
- Assertion Analysis: Tetracycline is a broad-spectrum antibiotic that inhibits bacterial translation, validating the Assertion.
- Reason Analysis: Tetracycline binds reversibly to the 30S ribosomal subunit of the bacterial 70S ribosome. This binding physically blocks the aminoacyl-tRNA from entering the acceptor (A) site, preventing the addition of new amino acids to the growing polypeptide chain, validating the Reason.
- Since this physical block of the ribosomal A-site explains how the drug inhibits protein synthesis, (R) is the correct explanation of (A).

Step 3: Final Answer:
Both (A) and (R) are true, and (R) is the correct explanation of (A).