Question

Mycoplasmas are different from the other prokaryotes by

• A. Presence of chitin in cell walls
• B. Presence of murrain in cell walls
• C. Presence of proteins in cell walls
• D. Absence of cell wall itself

Hint:

Mycoplasmas are prokaryotes that lack a cell wall, which makes them different from other bacteria and allows them to adopt various shapes.

Answer 1

The Correct Option is D

Step 1: Understanding Mycoplasmas.
Mycoplasmas are unique among prokaryotes because they lack a cell wall, unlike most other prokaryotes. This gives them flexibility in shape and makes them resistant to antibiotics that target cell wall synthesis.
Step 2: Analyzing the options.
(1) Presence of chitin in cell walls: Incorrect, mycoplasmas do not have chitin in their cell walls.
(2) Presence of murrain in cell walls: Incorrect, mycoplasmas do not have murrain in their cell walls.
(3) Presence of proteins in cell walls: Incorrect, mycoplasmas lack a cell wall entirely.
(4) Absence of cell wall itself: Correct — Mycoplasmas are unique due to the absence of a cell wall.
Step 3: Conclusion.
The correct answer is (4) Absence of cell wall itself.

Answer 2

Mycoplasmas are unusual prokaryotes distinguished by a specific structural feature. Let's check each option against what is actually known about their cell envelope.

1. Presence of chitin in cell walls: Chitin is a structural polysaccharide found in fungal cell walls and arthropod exoskeletons, not in prokaryotic cell walls, and mycoplasmas in particular have no cell wall at all.
2. Presence of murrain in cell walls: Most bacterial cell walls are built from peptidoglycan (sometimes referred to as murein), but mycoplasmas specifically lack this structure entirely, which is what makes them distinctive.
3. Presence of proteins in cell walls: While the mycoplasma cell membrane does contain proteins, this option implies a cell wall exists, which contradicts the defining feature of mycoplasmas.
4. Absence of cell wall itself: Mycoplasmas are bounded only by a plasma membrane, with no peptidoglycan or other cell wall layer at all, making this their defining structural distinction from other prokaryotes.

The defining structural feature of mycoplasmas is the complete lack of a cell wall.

Therefore, the correct answer is Absence of cell wall itself.