The main difference between plasmolysis and cytolysis is that in plasmolysis, water moves out of the cell due to hypertonic surroundings, whereas in cytolysis, water moves into the cell due to hypotonic surroundings.
Plasmolysis and cytolysis are two influences on the osmotic movement. They occur due to different osmotic pressure.
Key Areas Covered
1. What is Plasmolysis
– Definition, Features, Importance
2. What is Cytolysis
– Definition, Features, Importance
3. Similarities Between Plasmolysis and Cytolysis
– Outline of Common Features
4. Difference Between Plasmolysis and Cytolysis
– Comparison of Key Differences
Key Terms
Cytolysis, Plasmolysis
What is Plasmolysis
Plasmolysis is the condition of plant cells losing water from the cytoplasm. Generally, it occurs when a plant cell is placed in a hypertonic solution. Here, the solute concentration of the surrounding solution is higher than that of the cytoplasm. Therefore, the water potential of the cytoplasm is higher. Hence, water molecules move through the cell membrane to the outside solution until the inside and outside water potentials become equal. Also, the process of moving water through a semipermeable membrane, such as the cell membrane, is known as osmosis. Since this osmosis occurs towards the outside, it is known as exosmosis. Additionally, with the loss of water, the turgor pressure of the cytoplasm gradually drops.
Figure 1: Plasmolysis
Furthermore, based on the effect on the protoplasm, there are two types of plasmolysis. They are concave and convex plasmolysis. In concave plasmolysis, the protoplasm shrinks away from the cell wall, detaching it to form half-moon-shaped pockets in between. Generally, this condition can be reversed with the replacement of the plant cell in a hypotonic solution with a higher water potential. On the other hand, convex plasmolysis is more severe than concave plasmolysis. During this, the protoplasm completely detaches from the cell wall in a process called cytorrhysis. Generally, it is not reversible.
What is Cytolysis
Cytolysis is the process of cell burst due to the osmotic imbalance of the cell and the surrounding environment. In cytolysis, the surrounding environment of the cell is hypotonic and has a higher osmotic pressure. Therefore, water can enter the cell by diffusion. Water enters the cell through the cell membrane, which is a selectively permeable membrane with aquaporins that facilitates the movement of water through the cell membrane. The entrance of water into the cell causes the cell to increase its volume. When the water entrance exceeds the volume of the cell, it bursts. Also, cytolysis occurs in cells that do not have a cell wall, which prevents cells from bursting. Therefore, cytolysis occurs in animal and protozoan cells.
Figure 2: Cytolysis
Moreover, cells have different adaptations to prevent cell bursting. They include the presence of a contractile vacuole inside the cell that can fill up with water. Also, cells can rapidly pump the excess water out, preventing the building up of water inside the cell.
Similarities Between Plasmolysis and Cytolysis
- Plasmolysis and cytolysis are two influences on cells by the osmotic pressure of the surroundings.
- Water moves through diffusion from hypotonic to hypertonic compartments.
Difference Between Plasmolysis and Cytolysis
Definition
Plasmolysis refers to the contraction of the protoplast of a plant cell as a result of loss of water from the cell, while cytolysis refers to the cell burst due to an osmotic imbalance that has caused excess water to diffuse into the cell.
Significance
Water moves out of the cell due to hypertonic surroundings in plasmolysis, while in cytolysis, water moves into the cell due to hypotonic surroundings.
Fate of the Cell
The cell shrinks in plasmolysis, while the cell bursts in cytolysis.
Conclusion
In brief, plasmolysis and cytolysis are two processes that occur due to osmotic pressure. Plasmolysis is the contraction of the protoplast of the plant cell due to the water movement that occurs out of cells. It occurs due to the hypertonic surroundings. Also, it shrinks the cell. In comparison, cytolysis is the cell’s bursting due to water’s movement into the cell. It occurs due to the hypotonic surroundings. However, it bursts the cell. Therefore, the main difference between plasmolysis and cytolysis is the effect on the cell.
References:
- Editors, B. (2019, March 29). Plasmolysis – definition, types and examples. Biology Dictionary. https://biologydictionary.net/plasmolysis/
- Cytolysis. Biology Articles, Tutorials & Dictionary Online. (2021a, June 28). https://www.biologyonline.com/dictionary/cytolysis
Image Courtesy:
- “Blausen 0683 OsmoticFlow Hypertonic” By BruceBlaus– Own work (CC-BY 3.0) via Commons Wikimedia
- “Blausen 0684 OsmoticFlow Hypotonic” By BruceBlaus- Own Work (CC-BY 3.0) via Commons Wikimedia
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