Question

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Iodine is highly effective bactericidal agent and it is effective against all kinds of bacteria.
Reason (R) : Iodines are protein denaturants, and this property may to a large extent, account for their antimicrobial activity.
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:

Iodine-based disinfectants (like Betadine/Povidone-iodine) are known as iodophors.
They slowly release free iodine, which minimizes tissue irritation while maintaining powerful protein-denaturing and oxidizing capabilities against pathogens.

Answer 1

The Correct Option is A

Step 1: Concept:
The question evaluates the biological mechanism of iodine as a broad-spectrum antimicrobial agent and checks whether its protein-denaturing capability justifies its bactericidal efficiency.

Step 2: Step-by-step Explanation:

• Analyzing the Assertion (A): Iodine has long been used in clinical settings as a highly potent and fast-acting bactericidal agent.

• It exhibits a broad spectrum of activity and is highly effective against Gram-positive bacteria, Gram-negative bacteria, bacterial endospores (with sufficient exposure time), mycobacteria, and even many fungi and viruses.

• Therefore, the statement that it is a highly effective bactericidal agent effective against almost all kinds of bacteria is factually correct.

• Analyzing the Reason (R): The primary mechanism of action of elemental iodine involves penetrating the cell wall of microorganisms.

• Once inside, iodine acts as a strong oxidizing agent. It oxidizes the sulfhydryl (-SH) groups of amino acids (like cysteine) present in essential cellular enzymes.

• This massive oxidation leads to the irreversible denaturation and precipitation of cellular proteins and enzymes.

• Furthermore, iodine rapidly halogenates the phenolic rings of tyrosine residues within proteins, rendering them non-functional.

• Because the destruction of essential enzymatic proteins inherently kills the bacterial cell, this denaturing property directly accounts for its widespread antimicrobial activity.

• Thus, Reason (R) is correct, and it fundamentally provides the biological mechanism explaining Assertion (A).

Step 3: Final Answer:
Both statements are accurate, and R is the correct and logical explanation for why A occurs.