Answer:
When a red blood cell is placed in a hypertonic solution, it contracts as water is drawn out of the cell and into the surrounding solution. If the same blood cell is placed in a hypotonic solution, the blood cell grows in size. Blood cells in isotonic solutions do not shrink or swell.
The reason that blood cells change in size when placed in a solution with different salt concentration is due to the osmosis process. Osmosis causes solutions with high concentrations of salt to draw water from areas with low concentrations of salt.
There are some exceptions to this phenomenon. Blood cells can draw water and explode when placed in hypertonic solution on some special occasions. Some diseases affect the structural integrity of blood cells. Also, when human blood cells are exposed to temperatures close to freezing, they can draw water and explode.
Osmosis is an important phenomenon for living systems. The amount of salt in a given solution exhibits a tendency to diffuse through the environment, eventually resulting in equilibrium. In addition to blood cells, the kidneys function through the use of osmotic principles. The kidneys filter an animal's blood to remove excess salt and balance the amount of water
