Question

You placed the slide on the microscope immediately after adding the 10% NaCl solution to the Elodea cell and viewed no water movement across the plant cell membrane. However, upon returning shortly, you found that the plant cell membranes had shrunk. Which statements could be true? Select all that apply.

a. 10% NaCl is an isotonic solution.
b. 10% NaCl is a hypertonic solution.
c. You did not wait long enough to see the effects of osmosis.
d. Osmosis is not occurring in this plant cell.
e. The plant doesn't have chloroplast.

Answer 1

The correct explanations for the observed shrinkage of plant cell membranes in a 10% NaCl solution are that the solution is hypertonic, causing water to leave the cells, and that sufficient time was not given initially to observe the effects of osmosis.

Step-by-step explanation:

Upon observing that the plant cell membranes had shrunk after initially adding a 10% NaCl solution to the Elodea cells and seeing no water movement, there are several potential explanations. The correct statements are:

• b. 10% NaCl is a hypertonic solution: This means that the outside solution has a higher concentration of solutes (NaCl, in this case) compared to the inside of the cells, leading to water moving out of the cells to the environment, causing the cell membranes to shrink.
• c. You did not wait long enough to see the effects of osmosis: Osmosis can take some time to occur, and the initial absence of visible water movement doesn't mean osmosis isn't happening. It's just that the effects (cell membrane shrinking) took more time to become observable.

Since the plant cells lost water, indicated by the shrinkage of the cell membranes, we can determine that the solution was indeed hypertonic. The fact that the cells shrank (plasmolysis) also rules out the solution being isotonic since in an isotonic environment, cells would neither gain nor lose water.