In the context of osmosis, what effect does placing red blood cells in distilled water have on the cells?

• A. Water moves into the red blood cells, causing them to swell and potentially lyse (hemolysis).
• B. Water moves out of the red blood cells, causing them to shrink (crenation).
• C. Distilled water causes red blood cells to actively pump water out to maintain their volume.
• D. There is no net movement of water because distilled water is isotonic to red blood cells.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of osmosis, which is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.
2. Step 2: Recognize that red blood cells have a semipermeable membrane that allows water to move in and out but restricts many solutes.
3. Step 3: Identify the tonicity of distilled water relative to the inside of red blood cells. Distilled water has very low solute concentration (essentially zero), making it hypotonic compared to the cytoplasm of red blood cells.
4. Step 4: Apply the principle of osmosis: water will move from the hypotonic distilled water (low solute concentration) into the red blood cells (higher solute concentration) to try to equalize solute concentrations on both sides of the membrane.
5. Step 5: Understand the physiological consequence: as water enters the red blood cells, they swell and may eventually burst (lyse), a process called hemolysis.