- Account for the movement of substances across membrane using the concepts of osmosis.
- Apply the concept of osmosis to explain plasmolysis and haemolysis.
Mechanism of osmosis 💧
Osmosis is a net movement of water molecules through a semipermeable membrane from lower concentration region (higher water potential) to higher concentration region (lower water potential).
Water potential 👉🏻 the measure of potential energy of water which is the force to drive the water movement.
👆🏻 This photo demonstrating how osmosis occurred through a semipermeable membrane (cell membrane).
There are three types of solution which may affect the movement of water in osmosis❗️
👆🏻 This is the effect of isotonic solution, hypotonic solution and hypertonic solution towards animal cell and plant cell.
1. Isotonic solution
- Isotonic solution is the solution has the same water potential as the cell.
- No net movement of water molecules into or out of the cell.
- The appearance of animal cell and plant cell don't have any changes.
2. Hypotonic solution
- Hypotonic solution is the solution has the higher water potential than the cell.
- Surrounding fluid with higher water potential while the cell with lower water potential.
- A net movement of water into the cell.
- 🐻 Animal cell will lyse and burst open. Further, heamolysis occurred in red blood cell.
- 🌱 Plant cell will become turgid but will not burst due to the thick cell wall.
Heamolysis - red blood cell rupturing under excessive water entering the cell and cause it burst.💥
3. Hypertonic solution
- Hypertonic solution is the solution has the lower water potential than the cell.
- Surrounding fluid with lower water potential while the cell with higher water potential.
- A net movement of water out of the cell.
- 🐻 Animal cell will become shrivel.
- 🌱 Plant cell will become shrivel and plasmolysis occurred.
Plasmolysis - cytoplasm shrinking away from the plant cell wall due to excessive water leaving the cell. 🍃
In HKDSE Biology examination, heamolysis and plasmolysis are two important concept under the topic osmosis ❗️ ❕
That's the end of this topic 👏🏻
References
- Editors, B. D. (2019, March 26). Osmosis. Retrieved from https://biologydictionary.net/osmosis/