Why do you think it is a good idea to soak wilted lettuce in cool water before serving it?
A.
The water is an isotonic solution relative to the cytoplasm in the plant cells, so they will gain water and the lettuce will become less wilted.
B.
The water is a hypertonic solution relative to the cytoplasm in the plant cells, so the plant cells will lose water and the lettuce will become crisper.
C.
Soaking the lettuce in water would have no effect.
D.
The water is a hypotonic solution relative to the cytoplasm in the plant cells, so the plant cells will gain water and the lettuce will become crisper.
The Correct Answer and Explanation is:
The correct answer is D. The water is a hypotonic solution relative to the cytoplasm in the plant cells, so the plant cells will gain water and the lettuce will become crisper.
Explanation:
When lettuce wilts, it loses water from its cells, leading to limp, less crisp leaves. The cell membrane of plant cells functions as a semi-permeable barrier, allowing water to pass in and out, depending on the concentration gradient between the cell’s interior and its external environment.
In this case, soaking wilted lettuce in cool water exploits the principle of osmosis, which is the movement of water across a semi-permeable membrane from an area of lower solute concentration (in this case, the water) to an area of higher solute concentration (inside the plant cells). The cytoplasm within the plant cells contains various solutes, including salts and sugars, making it a more concentrated solution than the water. This means that the water acts as a hypotonic solution compared to the cytoplasm. In a hypotonic environment, water will naturally move into the cells.
As water enters the lettuce cells, the cells regain their turgor pressure—the pressure exerted by the cell membrane against the cell wall as the vacuole fills with water. This increased turgor pressure helps restore the firmness and crispness of the leaves. The lettuce becomes less wilted and more palatable.
Answer choices B and C are incorrect because a hypertonic solution (choice B) would cause further dehydration by drawing water out of the cells, making the lettuce even more wilted. Choice C is also incorrect because soaking the lettuce in water does have a noticeable effect, as explained by the osmotic process. Choice A is incorrect because the external water is not isotonic; it’s hypotonic relative to the cytoplasm.
This process is a practical application of osmosis in everyday life, restoring the texture of wilted lettuce to make it crisp and fresh again.