Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Protein synthesis is a central function in cellular physiology and is the primary target of many naturally occurring antibiotics and toxins. Tetracyclines are a class of broad-spectrum antibiotics used in the management and treatment of infectious disease by inhibiting translational machinery in bacteria. Reason (R): Tetracyclines inhibit protein synthesis in bacteria by blocking the A site on the ribosome, preventing the binding of aminoacyl tRNA. In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A) \
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A) \
• C. (A) is correct but (R) is not correct \
• D. (A) is not correct but (R) is correct

Hint:

Tetracycline blocks the A site, stopping the entry of Aminoacyl-tRNA. Without new amino acids, bacterial protein synthesis grinds to a halt.

Answer 1

The Correct Option is A

Step 1: Concept Translation is the process of protein synthesis where the genetic code in mRNA is read to build a polypeptide chain. Many antibiotics work by binding to bacterial ribosomes to disrupt this mechanism.

Step 2: Meaning The ribosomal A (Aminoacyl) site is the entry point for incoming charged tRNAs matching the next codon. Blocking this site stops the elongation of the protein chain.

Step 3: Analysis * Assertion (A) is correct: Translation is a vital metabolic process and a common target for antimicrobial drugs. Tetracyclines are well-known broad-spectrum antibiotics that specifically inhibit bacterial translation machinery. * Reason (R) is correct: Mechanistically, tetracyclines bind reversibly to the 30S ribosomal subunit of the bacterial 70S ribosome. This physically blocks the entry of aminoacyl-tRNA into the A site, preventing addition of new amino acids to the polypeptide chain. * Explanation assessment: The reason explicitly details the biochemical mechanism behind how tetracyclines disrupt translation, providing a direct explanation for the assertion.

Step 4: Conclusion Both statements are true, and (R) correctly explains how the antibiotic activity mentioned in (A) takes place. Final Answer: (A)