Question

unit 1.4 cell transport, homeostasis, feedback quiz 2025 a single plant cell is placed in an isotonic solution. salt is then added to the solution. which of the following would occur as a result of the salt addition? there would be no osmotic movement of water in response to the added salt. water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. water would enter the cell by osmosis, and the cell would swell. the added salt makes the solution hypotonic compared to the cell. water will enter the cell by osmosis.

Explanation:

1. First, recall the concept of osmosis and tonicity: An isotonic solution has the same solute concentration as the cell. When salt is added to the solution, the solute concentration of the solution increases, making it hypertonic relative to the plant cell.
2. In osmosis, water moves from an area of lower solute concentration (higher water potential) to an area of higher solute concentration (lower water potential). So, when the external solution becomes hypertonic (higher solute concentration) after adding salt, water will leave the plant cell (which has lower solute concentration compared to the new external solution) by osmosis.
3. Analyze each option:

• Option 1: Incorrect. Adding salt changes the tonicity, so there will be osmotic movement.
• Option 2: Correct. The added salt makes the solution hypertonic, so water leaves the cell by osmosis, and the cytoplasm volume (as the cell loses water) will decrease.
• Option 3: Incorrect. Water would leave, not enter, because the external solution is now hypertonic.
• Option 4: Incorrect. Adding salt increases solute concentration, making the solution hypertonic, not hypotonic, so water would leave, not enter.

Answer:

Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.