Question

Read the assertion and reason carefully to mark the correct option in question


Assertion: Gram-negative bacteria do not retain the stain when washed with alcohol.

Reason: The outer face of the outer membrane of gram-negative bacteria contains lipopolysaccharides, a part of which is integrated into the membrane lipids.

• A. If both assertion and reason are true but the reason is not the correct explanation of the assertion.
• B. If both assertion and reason are false.
• C. If both assertion and reason are true and the reason is the correct explanation of the assertion.
• D. If assertion is true but reason is false.

Answer 1

The correct option is C If both assertion and reason are true and the reason is the correct explanation of the assertion.

Elaboration:

The outer membrane of the gram positive bacteria comprises of peptidoglycan, whereas in the gram negative bacteria the outer membrane does not consist of peptidoglycan, instead is composed of lipopolysaccharides. Peptidoglycan present in the cell wall of the gram positive bacteria is responsible for staining. But in gram negative bacteria the stain is not retained as the lipopolysaccharides are alcohol soluble molecule, thus they get dissolved during the alcohol wash. Hence, assertion and reason are true and the reason is the correct explanation for the assertion.

Final answer: (A) If both assertion and reason are true and the reason is the correct explanation of the assertion.