Some students used vinegar to dissolve away the shells of three eggs and used these eggs as models of human red blood cells. The students observed the changes in the eggs when they were placed in different solutions.

Which statement best describes the role of the cell membrane in this model?

answer choices

A) The cell membrane is an impermeable barrier that prevents water from entering the cell.

B) The cell membrane allows solutes to enter the cell, which causes the cell to shrink.

C) The cell membrane allows water to enter and leave the cell.

D) The cell membrane removes solutes from the environment.

C) The cell membrane allows water to enter and leave the cell.

Explanation:

The cell membrane is a selectively permeable membrane that allows certain non-polar and small substances to move through it. Water is allowed to move freely through the cell membrane according to the concentration gradient. After the removal of shells, the membrane served as the outer most covering of eggs.

When placed in a different solution, the water moved in or out of the cells depending upon the concentration gradient. If the egg cells were placed in a hypotonic solution, water will enter into the egg cell resulting in the increase in its volume. On the other hand, when an egg cell is placed in a hypertonic solution, water leaves the cell through the cell membrane and the egg shrinks. This passive movement of water through the cell membrane is called osmosis.