Living Environment Regents Practice Test

After observing elodea cells in different salt solutions, which observation would most likely be made after five minutes?

1. Water had moved into the cells of slide A

2. Water had moved out of the cells of the leaf on slide B

3. The salt concentration equalized in both slides

4. The cells on slide A shrank significantly

The correct answer is: Water had moved out of the cells of the leaf on slide B

The observation that water had moved out of the cells of the leaf on slide B is grounded in the principles of osmosis, particularly in a hypertonic environment. When elodea cells are placed in a salt solution, the external concentration of salt is higher than that inside the cells, creating a hypertonic situation. In this scenario, water will move out of the cells toward the area with a higher concentration of solute (salt) to balance the concentration gradient. As water exits the cells, the cells lose turgor pressure, causing them to shrink. This process can lead to the observable effects in slide B, where the elodea cells will look plasmolyzed—meaning the cell membrane detaches from the cell wall due to the loss of water. This effect is common in plant cells subjected to hypertonic solutions and is a clear result of osmosis acting upon the concentration differences. In contrast, the other options suggest processes that would not occur in the described hypertonic environment, such as water entering the cells or an equalization of salt concentrations, which would require different conditions. Thus, observing the movement of water out of the cells in the leaf on slide B aligns with the expected behavior of plant cells in