Final answer:
When a red blood cell is placed in an isotonic solution, it will neither shrink nor swell because the solute concentration is the same inside and outside of the cell, resulting in no net movement of water.
Step-by-step explanation:
Osmosis involves the diffusion of water molecules across a selectively permeable membrane due to a difference in solute concentration on either side of the membrane. When a red blood cell is placed in an isotonic solution, it experiences no net movement of water into or out of the cell, because the solute concentration is the same both inside the cell and in the surrounding fluid. Therefore, the cell will neither shrink (crenate) nor swell and burst (lyse).
In a hypertonic solution, the exterior fluid has a higher solute concentration than the cell's cytosol, leading to water moving out of the cell, causing it to shrivel, a condition known as crenation. Conversely, in a hypotonic solution, the exterior fluid has a lower solute concentration, leading to water entering the cell, which can cause the cell to swell and potentially lyse.
Maintaining an isotonic environment is crucial for the survival of animal cells, including red blood cells, in order to prevent the damaging effects of excessive osmotic pressure. Organ systems such as the kidneys play a vital role in osmoregulation to maintain this balance.