Lab on Basic Cell Structure
Planning A: Background and Problem: Discuss the cell theory and then state the problem addressed in this lab. Hypothesis: What do you think would be a cellular difference between plant and animal cells? Variables: None Planning B: MATERIALS: Microscope, microscope slide, microscope cover slide, toothpick, forceps dropper pipette, iodine (*WARNING: iodine stains skin and clothing), and Elodea aquarium plant leaf. PROCEDURES: Part 1 1. 2. 3. 4. 5. Clean the lenses on your microscope using lens paper only. Prepare a wet mount of a single Elodea leaf. Examine the leaf on scanning, center focus and switch to low power. Center, focus and switch to high power. Using the fine adjustment knob focus on the layer of cells that have moving chloroplasts.
Draw four or five cells (i.e. don’t fill up a whole circle with squares) and label the following cellular structures: cell wall, cell membrane (not visible but you should label where it should be) chloroplasts, and cytoplasm. Answer questions a-f (in complete sentences) in data and results section of lab. a. How many cell layers thick is the leaf? *Focus up and down to determine this. You’re approximating so this introduces errors. b. Describe the color and shape of the chloroplast. c. What is the function of the chloroplasts? d. In which direction are the chloroplasts moving? if they are moving e. What do we called the movement and what structures are responsible for this movement? See notes on centrioles from hyperstudio stack
f. Why is it beneficial for the chloroplasts to move rather than remain stationary in the cell? 8. Part 2 1. 2. Use a clean toothpick to gently scrape the inside of your cheek. Smear the toothpick with the small piece of cheek tissue on the surface of your microscope slide. Make sure the smear forms a very thin layer on the surface of the slide. Return the microscope to scanning power before removing the slide. Dry slide and cover slip for part 2.
** You may not see much on the toothpick; however there will be hundreds of cells. 3. Place one drop of iodine on the top of the smear.
** Remember iodine will stain clothing and skin. 4. 5. 6. Place the a cover slide over the smear as you would with a regular wet mount. Following the proper procedure, examine the slide under high power. Draw and label the following structures of the cheek cell: cell membrane, nucleus and cytoplasm. Answer questions g-j. g. Why did you use iodine? h. Why was it important to make a thin smear? i. j. 7. Why are cheek cells all different shapes compared to boxes of plant cells? What structure(s) determines the shape of your cheek cell?
Did you clean, dry and return all materials? Did you return the microscope to scanning power before you removed the slide? Be sure your lab station is clean and dry or you will lose 25% on this lab write-up.
List all of your answers to the questions in the Data Processing and Presentation section. Conclusions and Evaluation l. 2. 3. Based on your observations from this lab, not from the textbook, list at least three observable differences between plant and animal cells. Error analysis Suggestions