Materials

Compound microscope

Microscopic slides and coverslips

Prepared slides of Rhodospirillum rubrum (prokaryotic)

Prepared slides of Anabaena or Nostoc (prokaryotic)

Toothpicks and razor blades

Dropper bottles of methylene blue dye, iodine solution, and water

Fresh onion (plant cell) and live Elodea (plant cell)

Beaker of disinfectant solution (10% bleach)

Methods

• Microscope Testing:

  • Place the “letter e” slide on the stage and locate it under low power to practice focusing.

• Observation of Rhodospirillum rubrum (Prokaryotic Cell):

  • Examine the prepared slide under the microscope.

  • Observe red, spiral, snake-like aggregates characteristic of bacterial cells.

• Observation of Anabaena or Nostoc (Prokaryotic Cell):

  • Observe the blue-green cyanobacteria, noting their filamentous structure and lack of a defined nucleus.

• Observation of Human Cheek Cells (Animal Cells):

  • Place a drop of methylene blue on a clean slide.

  • Gently scrape the inside of your cheek with a toothpick and mix the sample into the dye.

  • Cover with a coverslip and observe squamous epithelial cells with a distinct nucleus and “fried egg” appearance.

• Observation of Onion Cells (Plant Cells):

  • Place a thin slice of onion on a slide, add two drops of iodine solution, and cover with a coverslip.

  • Observe the rectangular cell shape and clearly visible cell wall and nucleus.

• Observation of Elodea (Plant Cells):

  • Observe chloroplasts and cell walls under the microscope.

Results

1. Rhodospirillum rubrum (Prokaryotic Cell)
Under the microscope, Rhodospirillum rubrum appeared as red, spiral-shaped or snake-like aggregates. The cells lacked a true nucleus and membrane-bound organelles. Their simple structure and shape were consistent with typical prokaryotic cells, which contain a cell wall composed of peptidoglycan but no chloroplasts or mitochondria.

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2. Anabaena or Nostoc (Prokaryotic Cell)
The Anabaena or Nostoc sample showed blue-green filaments made up of chains of cells. These cyanobacteria did not have a defined nucleus but contained photosynthetic pigments, allowing them to perform photosynthesis even without chloroplasts. Their structure demonstrated another form of prokaryotic organization, with each cell performing basic life functions independently.

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3. Human Cheek Cells (Eukaryotic Animal Cells)
The cheek cell slide revealed large, irregularly shaped squamous epithelial cells. Each cell had a clearly visible nucleus stained dark blue by methylene blue dye. The cytoplasm was visible around the nucleus, and no cell wall was present—only a flexible plasma membrane. These observations confirmed the eukaryotic nature of animal cells, which contain a nucleus and membrane-bound organelles.

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4. Onion Cells (Eukaryotic Plant Cells)
The onion cell sample displayed rectangular cells arranged in a grid-like pattern. The iodine stain highlighted the nucleus and cell wall clearly. The rigid structure of the cell wall provided shape and support. No chloroplasts were visible since the onion bulb grows underground, where photosynthesis does not occur.

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5. Elodea Cells (Eukaryotic Plant Cells)
Elodea cells were rectangular and contained numerous green chloroplasts that moved within the cytoplasm due to cytoplasmic streaming. The thick cell wall and central vacuole were also visible. These features demonstrated the main characteristics of plant cells, including photosynthesis and structural rigidity.