Question

A solution with an osmolarity of 400 mOsm/kg is separated from a cell with an osmolarity of 300 mOsm/kg by a semipermeable membrane. What will happen to the cell size?

a. The cell will swell.
b. The cell will shrink.
c. The cell size will remain the same.
d. The cell will burst.

Answer 1

The cell with lower osmolarity will lose water to the hypertonic surrounding solution, causing it to shrink.

Step-by-step explanation:

When a cell has a lower osmolarity (300 mOsm/kg) compared to its surrounding solution (400 mOsm/kg), this indicates that the surrounding solution is hypertonic. According to osmosis, water moves from areas of lower solute concentration to areas of higher solute concentration. Therefore, water will move out of the cell into the surrounding solution to balance the concentration of solutes. Due to this, the cell will shrink as it loses water, a process known as crenation in red blood cells. This movement is similar to what happens when red blood cells are placed in a hypertonic solution, where they also shrink due to water leaving the cell.