observation Human Epithelial Cells Epithelial cells cover the body\'s surface an
ID: 86728 • Letter: O
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observation Human Epithelial Cells Epithelial cells cover the body's surface and line its cavities. Figure 2.12 Cheek epithelial cells. Label the nucleus, the cytoplasm, and the plasma 1. obtain a prepared slide, or make your own as follows: a. obtain a prepackaged flat toothpick (or sanitize one with alcohol or alcohol swabs). b. Gently scrape the inside of your cheek with the toothpick, and place the scrapings on a clean, dry slide. Discard t used toothpicks in the biohazard waste container provided. c. Add a drop of very weak methylene blue or iodine solution, and cover with a coverslip. 2. Observe under the microscope. 3. Locate the nucleus (the central, round body), the cytoplasm, and the plasma membrane (outer cell boundary). Label Figure 2.12. 4. Because your epithelial slides are biohazardous, they must be disposed of as indicated by your instructor. 5. Note some obvious differences between the onion cells and the human cheek cells, and list them in Table 2.5. Table 2.5 Differences Between Onion Epidermal and Human Epithelial Cells Human Epithelial Cells (Cheek) Onion Epidermal Cells Observation: Euglena Examination of Euglena (a unicellular organism with a flagellum to facilitate movement) will test your ability to utilize depth of field and to control illumination in order to heighten contrast. 1. Make a wet mount of Euglena by using a drop of a Euglena culture and adding a drop of Protoslo (methyl cellulose solution) onto a slide. The Protoslo slows the organism's swimming. 2. Mix thoroughly with a toothpick, and add a coverslip, 3. Scan the slide for Euglena: Start at the upper left-hand corner, and move the slide forward and back as you work across the slide from left to right. The Euglena may be at the edge of the slide because they show an aversion to Protoslo 4. Experiment by using scanning, low-power, and high-power objective lenses; by focusing up and down with the fine-adjustment knob; and by adjusting the light so that it is not too bright. 5. Compare your Euglena specimens with Figure 2.13 (top left). List the labeled features that you can actually see. Laboratory 2 Metric Measurement and Microscopy 25Explanation / Answer
Observation Human Epithelial cells
3. 1. Plasma membrane, 2. nucleus, 3. Cytoplasm.
5. Onion Epidermal cell and Human epithelial cell
Shape: onion epidermal cells are rectangular and cheek cells are spherical
Orientation: cytoplasm of a cheek cell is more granular, is denser and occupies a larger space than the cytoplasm of an onion epidermal cell. The positioning of Nucleus is at the periphery of an onion cells’ cytoplasm while the nucleus of a cheek cell is positioned centrally.
Boundary: Onion has a cell wall and human cheek cell does not.
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