Question

what is happening to the elodea cell that is causing it to shrink

a. due to the hypotonic solution, water is leaving the cell.
b. due to the isotonic solution, water is leaving the cell.
c. due to the hypertonic solution, water is leaving the cell.
d. due to the hypertonic solution, water is entering the cell.

Explanation:

Analyze the cell's physical change

The question asks what is causing the Elodea cell to shrink. When a plant cell like Elodea shrinks, its plasma membrane pulls away from the rigid cell wall. This specific biological phenomenon is known as plasmolysis.

Apply tonicity and water movement principles

Using the Osmosis Principles knowledge point

$$ \Psi_{\text{outside}} < \Psi_{\text{inside}} \implies \text{Net water movement is outward} $$

• A cell shrinks because it loses water to its surroundings.
• Water moves from an area of lower solute concentration (higher water potential) to an area of higher solute concentration (lower water potential).
• Therefore, the surrounding environment must have a higher solute concentration than the inside of the cell.

Identify the correct solution type

• A solution with a higher solute concentration relative to the cell's cytoplasm is defined as hypertonic.
• In a hypertonic solution, water leaves the cell via osmosis, causing the vacuole and cytoplasm to shrink.
• This matches option C: "Due to the hypertonic solution, water is leaving the cell."

Evaluate the incorrect options

• Option A is incorrect because a hypotonic solution has a lower solute concentration, which would cause water to enter the cell and make it turgid.
• Option B is incorrect because an isotonic solution has an equal solute concentration, resulting in no net movement of water.
• Option D is incorrect because water leaves the cell, rather than entering it, when placed in a hypertonic solution.

Answer:

• (A) Due to the hypotonic solution, water is leaving the cell.
• (B) Due to the isotonic solution, water is leaving the cell.
• (C) Due to the hypertonic solution, water is leaving the cell. (Correct answer)
• (D) Due to the hypertonic solution, water is entering the cell.