Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Mycoplasmas are pleomorphic in shape
Reason R: Cell wall in Mycoplasmas is flexible
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:

Mycoplasmas are the only prokaryotes that naturally lack a cell wall. This absence makes them completely pleomorphic and naturally resistant to cell-wall-targeting antibiotics like penicillin.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Mycoplasmas are a unique genus of bacteria that differ structurally from other prokaryotes.
Their lack of a rigid cell wall significantly influences their physical properties and resistance to certain classes of antibiotics.

Step 2: Detailed Explanation:
Assertion A Analysis: Mycoplasmas are highly pleomorphic, meaning they do not possess a single, fixed morphology.
Instead, they can assume various irregular shapes, ranging from spherical or pear-shaped to filamentous and branched structures. Thus, Assertion A is correct.
Reason R Analysis: The cell wall is the structural component that determines and maintains the shape of a bacterial cell.
Mycoplasmas are characterized by the complete absence of a cell wall.
Instead of a flexible cell wall, they are bounded only by a three-layered, sterol-rich cytoplasmic membrane.
Because they lack a cell wall entirely, they are free to deform and alter their shape.
Thus, the assertion that the "cell wall in Mycoplasmas is flexible" is factually incorrect because they do not have a cell wall at all.
Since Assertion A is true and Reason R is false, the correct option is (C).

Step 3: Final Answer:
Hence, A is true but R is false.