Briefly Define "Isotonic," "Hypotonic," and "Hypertonic" Solutions

Question

Examlex · Accepted Answer

The Answer is (a) Definitions:

- Isotonic Solution: An isotonic solution is one where the concentration of solutes is equal both inside and outside the cell. This results in no net movement of water across the cell membrane, maintaining the cell's shape and volume.

- Hypotonic Solution: A hypotonic solution has a lower concentration of solutes compared to the inside of the cell. This causes water to move into the cell by osmosis, potentially leading to cell swelling and possibly bursting if the influx is excessive.

- Hypertonic Solution: A hypertonic solution has a higher concentration of solutes than the inside of the cell. This causes water to move out of the cell, leading to cell shrinkage or crenation as the cell loses water.

(b) Cellular Response in Different Solutions:

- In an Isotonic Solution: When a cell is placed in an isotonic solution, there is no net movement of water into or out of the cell. The cell remains in equilibrium with its environment, and its shape and volume are maintained. This is the ideal situation for most cells, as it does not disrupt their normal function.

- In a Hypotonic Solution: When a cell is placed in a hypotonic solution, water enters the cell due to the higher solute concentration inside the cell compared to the surrounding solution. As water flows into the cell, it swells and may eventually burst in a process called lysis if the cell wall is not strong enough to withstand the pressure. This is particularly a concern for animal cells, which lack a rigid cell wall. Plant cells, on the other hand, have a cell wall that provides structural support and prevents them from bursting, though they may become turgid, which is a healthy state for plant cells.

- In a Hypertonic Solution: When a cell is placed in a hypertonic solution, water moves out of the cell to the surrounding solution where the solute concentration is higher. This results in the cell shrinking or crenating. In plant cells, this can lead to plasmolysis, where the cell membrane pulls away from the cell wall as the cell loses water. This can be detrimental to the cell, as it can impair cellular processes and may lead to cell death if the dehydration is severe.