Question

If a red blood cell (intracellular concentration of $0.9\%$ salt) was placed into a test tube containing $10\%$ salt solution, what would happen to it?

• A. It would fill with water and burst.
• B. Nothing - the solution is isotonic to the interior of the red blood cell
• C. The red blood cell would shrink as it loses water to the salt solution in the test tube.
• D. None of these

Answer 1

The correct option is C

The red blood cell would shrink as it loses water to the salt solution in the test tube.

The intracellular concentration of the RBC is more dilute or hypotonic compared to the salt solution. Hence, the salt solution acts as a hypertonic solution when compared to the RBC. Therefore, water will move out of the RBC by exosmosis and will result in the shrinking of the RBC (Water moves from a hypotonic solution to a hypertonic solution).