Investigation 4 – PostLab
Note: Questions marked with a triangle (∆) are included to enrich students’ understanding. These questions do not appear in your SDR but should be used as additional discussion points during the PostLab.
- ∆ How would you describe the solute contents of the liquids you used to mount the onion or Elodea specimens?
- ∆ Instruct students to describe what occurred in the Elodea leaf when placed in liquids with successively higher concentrations of salt. What did you observe?
- Instruct students to describe what occurred in the onion. What did you observe?
- What conclusions can you draw from your experiments concerning the permeability of the Elodea and onion cell to water and sodium chloride? Are the membranes permeable to water? To sodium chloride?
Compare your observations of the onion cell and the cells in the Elodea leaf.
- Which was easier to observe, the cells in the onion or the Elodea leaf?
- The color of the Elodea leaf likely made it easier for you to view the effects of osmosis. Does the Elodea leaf contain color due to the staining of the slide or to the natural characteristics of the cells?
Complete the Analysis Questions in your SDR then discuss them as a class.
- Why did the cytoplasm and cell membranes shrink when the cells were placed in the salt solutions?
- Why didn’t the cells shrink as they were placed in the tap water?
- Compare the reaction of the cells to the 2% solution to the reaction to an 8% solution. Explain your observations.
Complete the Focus Questions in your SDR then discuss them as a class.
- Is the cell membrane of a plant cell permeable to salt?
- Are the cell wall and the cell membrane of a plant cell permeable to water?
- How does the structure of the cell wall and cell membrane affect the movement of substances in and out of a cell?