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Presentation/PPT
27/08/2022
Pre-Lab Questions
Experiment 1: Cell Structure and Function
The structure of a cell dictates the majority of its function. You will view a selection of slides that exhibit unique structures that contribute to tissues function.
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Materials: Onion (allium) Root Digital Slide Images |
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Procedure
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Onion Root Tip: 100X |
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Onion Root Tip: 1000X |
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Onion Root Tip: 1000X |
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Onion Root Tip: 100X. Each dark circle indicates a different nucleus. |
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Onion Root Tip: 1000X |
Post-Lab Questions
1. Label each of the arrows in the following slide image: A=Chromosomes, B=Nucleus, C=Cytoplasm, D=Cell Wall
2. What is the difference between the rough and smooth endoplasmic reticulum?
3. Would an animal cell be able to survive without a mitochondria? Why or why not?
4. What could you determine about a specimen if you observed a slide image showing the specimen with a cell wall, but no nucleus or mitochondria?
5. Hypothesize why parts of a plant, such as the leaves, are green, but other parts, such as the roots, are not. Use scientific reasoning to support your hypothesis.
Experiment 2: Osmosis – Direction and Concentration Gradients
In this experiment, we will investigate the effect of solute concentration on osmosis. A semi-permeable membrane (dialysis tubing) and sucrose will create an osmotic environment similar to that of a cell. This selective permeability allows us to examine the net movement of water across the membrane. You will begin the experiment with a 30% sucrose solution, and perform a set of serial dilutions to create lower concentration solutions. Some of the sucrose concentrations will be membrane permeable; while others will not be permeable (can you determine why this is?).
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Materials (3) 250 mL Beakers |
*Stopwatch *You Must Provide *Be sure to measure and cut only the length you need for this experiment. Reserve the remainder for later experiments. |
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Procedure
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Table 2: Serial Dilution Instructions |
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Sucrose Solution |
mL of Stock Sucrose Solution Needed |
mL of Water Needed |
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30% |
10 |
0 |
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15% |
5 |
5 |
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3% |
1 |
9 |
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3% |
1 |
9 |
Hint: Use your knowledge of serial dilutions to create this final, 3% sucrose solution.
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Figure 8: The dialysis bags are filled with varying concentrations of sucrose solution and placed in one of two beakers. |
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Table 3: Sucrose Concentration vs. Tubing Permeability |
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Band Color |
Sucrose % |
Initial Volume (mL) |
Final Volume (mL) |
Net Displacement (mL) |
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Yellow |
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Red |
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Blue |
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Green |
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Hypothesis:
Post-Lab Questions
1. For each of the tubing pieces, identify whether the solution inside was hypotonic, hypertonic, or isotonic in comparison to the beaker solution in which it was placed.
2. Which tubing increased the most in volume? Explain why this happened.
3. What do the results of this experiment this tell you about the relative tonicity between the contents of the tubing and the solution in the beaker?
4. What would happen if the tubing with the yellow band was placed in a beaker of distilled water?
5. How are excess salts that accumulate in cells transferred to the blood stream so they can be removed from the body? Be sure to explain how this process works in terms of tonicity.
6. If you wanted water to flow out of a tubing piece filled with a 50% solution, what would the minimum concentration of the beaker solution need to be? Explain your answer using scientific evidence.
7. How is this experiment similar to the way a cell membrane works in the body? How is it different? Be specific with your response.
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