AIIMS 2009 Botany Mycoplasma MCQ Question

Correct Answer: B) Cell membrane

The outermost limiting layer of mycoplasma is primarily composed of a cell membrane. Unlike many bacteria that have a rigid cell wall made of peptidoglycan, mycoplasma species possess a flexible plasma membrane. This membrane is primarily made up of phospholipids and proteins, which allow for selective permeability and the maintenance of the internal environment of the cell.

Key Reasons:

1. Lack of Cell Wall: Mycoplasma are known for their absence of a cell wall, which is a significant characteristic. This absence makes them more susceptible to osmotic pressure changes but allows them to be highly adaptable to various environments.
2. Cell Membrane Functionality: The cell membrane in mycoplasma is responsible for various cellular functions, including transport, communication, and energy production. It also plays a crucial role in maintaining the structural integrity of the cell.

Clarifying Incorrect Options:

• A) Cell wall: Mycoplasma do not have a cell wall, which is a defining characteristic. This option is incorrect because the presence of a cell wall is typical for many other bacteria but not for mycoplasma.

• C) Mucilaginous sheath: While some bacteria may produce a mucilaginous sheath, this is not a characteristic feature of mycoplasma. A mucilaginous sheath can be found in certain bacterial species that protect them from environmental stress, but it does not represent the outermost layer of mycoplasma.

• D) Slime layer: Similar to the mucilaginous sheath, a slime layer is generally associated with certain bacteria that secrete a protective layer of polysaccharides. Mycoplasma lack this structure as well. The slime layer is not an anatomical feature of mycoplasma, making this option incorrect.

Conclusion:

In summary, the correct answer is B) Cell membrane because it is the sole limiting layer in mycoplasma due to their unique lack of a cell wall. Understanding the structure of mycoplasma is essential in microbiology and can help in the development of targeted antibiotics, as their unique characteristics often make them resistant to standard treatments that target cell wall synthesis.