JNTU B.Pharmacy II PHARMACEUTICAL MICROBIOLOGY Previous Question Paper (April - 2023 - R17)

The primary differences between prokaryotes and eukaryotes are as follows:

• Nucleus: Prokaryotes lack a membrane-bound nucleus, with DNA existing in a nucleoid region, whereas eukaryotes possess a distinct, membrane-bound nucleus containing genetic material.
• Organelles: Prokaryotes lack membrane-bound organelles such as mitochondria, endoplasmic reticulum, or Golgi apparatus, while eukaryotes contain these specialized structures.
• Cell Structure: Prokaryotic cells are generally smaller and simpler, typically unicellular, while eukaryotic cells are larger, more complex, and can be either unicellular or multicellular.

Dark field microscopy is a specialized technique used to enhance the contrast of unstained, transparent, or living microorganisms that are difficult to visualize under conventional bright-field microscopy. It operates by utilizing a modified condenser that blocks the central light rays, allowing only oblique or peripheral light to strike the specimen.

The key principles and applications include:

• Principle: The specimen is illuminated from the sides by light rays that do not enter the objective lens directly. Only light scattered by the specimen enters the objective, resulting in a bright object appearing against a dark background.
• Application: This method is particularly useful for observing highly motile organisms and delicate structures, such as Treponema pallidum, the causative agent of syphilis, which is too thin to be seen clearly with standard staining techniques.
• Advantage: It allows the observation of live, unstained specimens in their natural state, avoiding the potential artifacts introduced by heat fixation or chemical staining.