Difference Between Plasmolysis and Cytolysis

Key Difference – Plasmolysis vs Cytolysis
 

When a cell is immersed in a solution, there is an osmotic pressure that builds up between the cell and the solution. Depending upon the nature of the solution, the cell undergoes two physical changes, namely plasmolysis and cytolysis. When the cell is immersed in a hypertonic solution, the cell loses water to the external environment. Thus the protoplasm tends to peel away from the cell wall. This process is referred to as plasmolysis. When the cell is immersed in a hypotonic solution, the cell will gain water into the cell through endosmosis. This will result in an increase of volume inside the cell. The continuous flow of water into the cell will result in cell bursting that is referred to as cytolysis. The key difference between the two processes is the type of solution in which the cell is immersed in. For plasmolysis to take place the cell should be immersed in a hypertonic solution, whereas for cytolysis to take place the cell should be immersed in a hypotonic solution.

CONTENTS

1. Overview and Key Difference
2. What is Plasmolysis
3. What is Cytolysis
4. Similarities Between Plasmolysis and Cytolysis
5. Side by Side Comparison – Plasmolysis vs Cytolysis in Tabular Form
6. Summary

What is Plasmolysis?

A hypertonic solution is a solution in which the solute concentration is high, and the water concentration is low. In other words, the hypertonic solution has higher solute potential and low water potential than the cell. Therefore, according to the phenomenon of Osmosis, water molecules move across a concentration gradient via a semi-permeable membrane from higher water potential to lower water potential. Hence, when a cell is placed in a hypertonic solution, water will flow out of the cell in order to get the ionic concentration of the internal and external environment to equilibrium. This process is referred to as exosmosis. Until the water potentials are balanced, water will move out of the cell to the solution. During this process, the protoplasm starts to detach from the cell wall. This is known as plasmolysis.

In certain organisms, where there is no cell wall, plasmolysis can be fatal and can lead to the destruction of the cell. Plasmolysis takes place under extreme pressure and can be induced under laboratory conditions by using high concentrated saline solutions.

Plasmolysis can be mainly of two types; Concave plasmolysis and convex plasmolysis. Concave plasmolysis is reversible. During concave plasmolysis, the plasma membrane does not completely detach from the cell wall, instead remains intact. Convex plasmolysis is irreversible and is the extreme level of plasmolysis where the cell plasma membrane completely detaches from the cell wall. This can lead to complete destruction of the cell.

What is Cytolysis?

Cytolysis is a phenomenon that occurs with the bursting of a cell due to the development of a condition of osmotic imbalance. Due to this imbalance in the osmotic pressure, the excess water into the cell is diffused. In-depth analysis of this phenomenon reveals that the entering of water into the cell is facilitated by aquaporins, which are selective membrane channels. The mechanism of entering of water into the cell is the diffusion. Diffusion occurs through the cell membrane. Cytolysis occurs when the outside environment is hypotonic, and excess of water enters the cell up to a level where it breaks the threshold of the cell membrane or aquaporin. The destruction of the cell membrane is referred to as cell burst.

In the context of mammals, cytolysis often occurs due to improper nutrient intake and alterations in the waste removal mechanisms. These conditions lead to alteration in cell metabolism. Altered cell metabolism patterns lead to cytolysis since it develops an uneven balance of the osmotic pressure. Due to this, in mammals, extracellular fluid is moved into the cells that cause cytolysis. Even though it seems to be a harmful phenomenon, the immunity system of the human body utilizes this mechanism to initiate cell destruction processes when it comes to malignant cells.

To prevent the occurrence of cytolysis in cells, different organisms utilize different strategies. A contractile vacuole is used by Paramecium that involves the rapid pumping-out of the excess liquids built up within their systems. Presence of a cell membrane that is less permeable to water also allows certain species of organisms to prevent cytolysis.

What are the Similarities Between Plasmolysis and Cytolysis?

• Both plasmolysis and cytolysis occur in cells according to the type of solution in which the cell is immersed.
• Both plasmolysis and cytolysis cause for cell death.
• Both plasmolysis and cytolysis happen due to water movement across the cell membrane by osmosis.

What is the Difference Between Plasmolysis and Cytolysis?

Summary – Plasmolysis vs Cytolysis

When the cell is immersed in a hypertonic solution, the cell loses water to the external environment. Thus, the protoplasm shrinks and detaches from the cell wall. This process is referred to as plasmolysis. Plasmolysis can be mainly of two types. Concave plasmolysis or convex plasmolysis. When the cell is immersed in a hypotonic solution, the cell will gain water into the cell through endosmosis. This will result in an increase of volume inside the cell. The continuous flow of water into the cell will result in cell bursting is referred to as cytolysis. To prevent the occurrence of cytolysis in cells, different organisms utilize different strategies. This is the difference between plasmolysis and cytolysis.

Reference :

1.Editors. “Cytolysis – Definition, Types and Function.” Biology Dictionary, 28 Apr. 2017. Available here 
2.Editors. “Plasmolysis – Definition, Types and Examples.” Biology Dictionary, 29 Apr. 2017.  Available here 

Image Courtesy:

1.’OSC Microbio 03 03 Plasmolysi’By CNX OpenStax , (CC BY 4.0) via Commons Wikimedia  
2. ‘Osmotic pressure on blood cells diagram’By LadyofHats – Own work, (Public Domain) via Commons Wikimedia