Like most eukaryotic cells, this cell is very large compared to prokaryotic cells. For scale, notice the pair of dark blue bacteria cells sticking to the right edge of the cheek cell. The bacteria are only a fraction of the size of the nucleus, but their tiny size is typical for bacteria. This cell was stained blue and was magnified to x its normal size when it was photographed. Prokaryotic vs. Eukaryotic Cells. Whitson Home. Bio Home. In the diagram to the right, the average size of each cell is 0.
Cheek cells are eukaryotic cells cells that contain a nucleus and other organelles within enclosed in a membrane that are easily shed from the mouth lining. This is why plants are green. The simple answer is that plants are green because they have green chloroplasts organelles that carry out photosynthesis. Chloroplasts are green because they contain the green pigment chlorophyll in their thylakoid membranes.
Chlorophyll is a pigment that absorbs red and blue light. Plastids are not found in cheek cells. Because cheek cells are animal cells and animal cells don't show any pigmentation because they don't contain plastids. Cards Term Why should only lens paper be used to clean microscope lenses? Definition Microscope lenses scratch easily.
Term Where should an adjustable condenser be set for maximum resolution? Definition About 1mm away from the stage. The elodea like all green plants uses the process of photosynthesis to produce organic energy molecules. Oxygen is a by product of the process of photosynthesis. Oxygen can be observed leaving the elodea cells. Under a microscope the green chloroplasts inside of the cell can be observed.
Model Organisms The nucleus, for example, contains a cell's chromosomes, while mitochondria are the site of cellular respiration. Chloroplasts and mitochondria move within Elodea leaf cells ; nuclei are also visible as clear, fried-egg-shaped structures. Elodea are common freshwater aquarium plants. From the movement of chloroplasts they will infer that cyclosis, or protoplasmic streaming, is occurring.
They also will observe that most chloroplasts are pressed tightly against the cell wall and should infer from this that much of the cell is occupied by a vacuole. Elodea , , or In Elodea , cyclosis is easy to observe because chloroplasts move with the cytoplasm as it flows. Light and heat stimulate cyclosis in Elodea.
Tungsten or halogen substage microscope lamps produce both heat and light, so after 2—3 minutes, students should be able to observe the movement of chloroplasts.
If your microscopes have fluorescent or LED lamps, these produce very little heat and often will not stimulate cyclosis. To provide the needed heat, use a desk lamp equipped with a halogen bulb. Position the lamp so that it shines down on the lab bench. After a few minutes, the surface of the lab bench should become noticeably warm to the touch.
Students can place their slides on this warm surface for 3 minutes and then look for signs of cyclosis. A somewhat better arrangement is to position the lamp so that it shines directly onto the stage of a microscope, thereby heating the slide while students view it. Not all slides will show cyclosis, so have students share those that do, so that everyone has the opportunity see the movement. Ensure that students understand and adhere to safe laboratory practices when performing any activity in the classroom or lab.
Demonstrate the protocol for correctly using the instruments and materials necessary to complete the activities, and emphasize the importance of proper usage. Use personal protective equipment such as safety glasses or goggles , gloves , and aprons when appropriate. Model proper laboratory safety practices for your students and require them to adhere to all laboratory safety rules.
Although you can receive Elodea and use it the same day, it is much better to condition the plants under lights for 2 days. On the day of the lab set up 2 or more small tanks or large beakers, each containing water and Elodea. Place forceps and droppers alongside each container. Also, set up stations for pickup of microscope slides, coverslips, and dissecting needles.
Optional: If students have studied osmosis, they can observe plasmolysis. Students are unlikely to observe nuclei in Elodea cells. However, nuclei are easily observed in stained cells of onion skin. Quarter an onion and separate the layers. Use forceps to remove the skin from the inner concave surface of a layer. Cut or tear the onion skin into small pieces that will fit under a coverslip.
Place the onion skin on a microscope slide and smooth out as many wrinkles as possible. Add a drop of stain to cover the onion skin. A number of stains can be used, including iodine solutions iodine-potassium iodide , Lugol solution , Gram iodine , crystal violet , toluidine blue , and methylene blue. After 1 minute, rinse away the stain with tap water, add a coverslip, and observe the cells.
Nuclei will be evident. In addition to light and heat, pH also influences cyclosis. Have students conduct a study to determine at what pH cyclosis is most likely to occur. We use cookies to provide you with a great user experience.
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Show students the video of Elodea leaf cells. Which cellular structures can they observe? In discussing the moving chloroplasts, ask students if there are areas that the chloroplasts seem to avoid and what might account for this.
Replay the video if students would like to watch the chloroplasts more carefully. Play the video of Elodea leaf cells with structures labeled so students can check their understanding. Pass out the Elodea images , rulers, and student pages, then lead students in the explorations on the student pages. Note that student answers will vary depending on the cell they choose and their measurement technique.
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