Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A : Antibiotics are sterilized by bacteriological filters but not by heat
Reason R : Antibiotics are thermo labile compounds
In light of the above statements, 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:

Thermolabile substances (Vitamins, Antibiotics, Hormones) \( \rightarrow \) Filtration.
Thermostable substances (Salts, Agars, Glassware) \( \rightarrow \) Autoclave.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question concerns laboratory techniques for sterilization, specifically for substances used in tissue culture or microbiology media that are sensitive to temperature.

Step 2: Detailed Explanation:

• Assertion Analysis: Standard sterilization in a lab is done via autoclaving (heat and pressure).
However, if an antibiotic like Streptomycin or Ampicillin is added to the media before autoclaving, the high temperature will destroy its chemical structure and biological activity.
To maintain their potency, antibiotics are filter-sterilized using membrane filters (usually $0.22 \mu m$ pore size) and then added to cooled, pre-sterilized media.
Thus, Assertion A is True.

• Reason Analysis: The reason antibiotics cannot be heated is that they are thermolabile (heat-sensitive).
Heat provides enough kinetic energy to break the specific covalent bonds or denature the molecular conformation required for the antibiotic to function.
Thus, Reason R is True.

• Relationship: Since the heat-sensitivity (Reason) is the direct cause for choosing filtration over heat sterilization (Assertion), Reason R is the correct explanation of Assertion A.
Final Answer:
Both statements are correct, and the Reason provides the underlying chemical justification for the Assertion.