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Biology 203 Lab. Lab Report 1

Observation of Microscopic Cells Introduction In this experiment our main working tool was microscope which is used by biologists in the laboratory to magnify small objects and resolve fine details. In this case, we were using light microscope (LM), where visible light is passed through the specimen and then through glass lenses. The lenses refract (bend) the light in such a way that the image of the specimen is magnified as it is projected into the eye or into a camera (Campbell-Reece Biology, 10th edition). The purpose of this experiment is to make an observation over the Elodea leaves, onion epidermal cells and human cheek cells with LM. If experiment conducted properly, since the light microscope can enlarge the specimen 1000 times more than its size, it is expected that we can collect information about cell wall, cell type, cell shape, color and kingdom of the observed specimens. Materials and Methods Materials used in this experiment are: Light microscope, microscope slides and coverslips, lens paper, Pasteur pipette, methylene blue stain (0.5% ), iodine solution, elodea leaves, onion epidermal cells, human cheek cells, toothpick, DI water and normal saline (0.9%NaCl). Preparation procedure for wet mount of Elodea leaf: we are adding a leaf of elodea to the center of a microscope slide and then pouring drop of a DI water. After that we carefully lay a coverslip over the drop. After all is done, the specimen is ready to be examined in the LM. Preparation procedure for an onion epidermal cells: We add a drop of water at the center of the microscopic slide and then thin layer of the onion. After that, we pour on it a drop of iodine solution or the methylene blue on the onion membrane. Then, we carefully lay a coverslip over the drop, during this process air bubbles should be removed. Finally, we make an observation. Preparation procedure for human cheek cells: we place a drop of methylene blue stain on a slide and then using the broad end of a flat toothpick to gently scrape the inside of our cheek. After that, we transfer cheek cells to the slide by swirling the toothpick in the drop of methylene blue. We cover it with a cover slip and make an observation. Results

Elodea leaf Human check cells

Onion epidermal cells

Table 1-information based on the pictures Elodea leaf Present Eukaryotic Stiff cell, rectangular, box like shape

Onion epidermal cell Present Eukaryotic Elongated rectangular

Color

Green because of the chlorophyll

Pinkish red

Kingdom

Plantae

Plantae

Cell wall Cell type Cell shape

Human cheek cells Absent Eukaryotic Round, flat with a small nucleus, but still irregular shape Colorless, appears dark blue because stained with methylene blue Animalia

Discussion All the pictures obtained are reasonable and matches the general characteristics of plant and animal cells. In the picture of elodea leaf and onion epidermal cells we see the cell wall. It was expected, since the plant cell wall are much thicker than the animal cell wall and they are seen clearly in the light microscope, however since the Glicocalyx is much thinner it cannot be seen in the light microscope. We can observe chloroplasts in the elodea leaf. We see the cytoplasm and nucleus (and vacuole in plant cells) in the three of the cells, but there cannot be done deep observation on the organelles since the LM’s magnifying capabilities are not enough. Conclusion We used light microscope to observe three different cells: two plant cells of elodea leaf and onion epidermis and animal cell of human cheek. The results obtained were quite reasonable and clear as much as LM could make it. Experiment helped to once more detect distinctions between plant and animal cell and familiarize with general characteristics of different cells....