Diffusion is the net movement of molecules from higher concentration to lower concentration. All molecules diffuse except for water molecules. Do you know what we call the diffusion of water molecules? In this lesson we will be learning about the diffusion of water molecules.
Explanation:
Diffusion of water molecules is known as "osmosis". Osmosis is the net movement of water molecules from high water potential (high water concentration) to low water potential (low water concentration) through a partially permeable membrane.
Various factors affect the rate of osmosis:
The rate is increased at high temperatures as the molecules gain kinetic energy.
Small molecules diffuse faster through osmosis.
Steep concentration gradient. The steeper the concentration gradient the faster the rate.
Water molecules require a partially permeable membrane to diffuse, through the process of osmosis. There are three conditions according to which water molecules dissolve in living organisms:
In animal cells, there are 3 conditions.
Hypotonic condition
It means to have more solvent and less solute. If an animal cell is placed in a hypotonic solution then the water from the surrounding (high concentration) travels inside the cell (lower concentration) through a partially permeable membrane. The cell bursts because its delicate cell membrane can not bear the water pressure.
Hypertonic condition
It means to have more solute and less solvent. If an animal cell is placed in a hypertonic solution then the water from the cell (high concentration) travels to the surrounding (lower concentration) through a partially permeable membrane. The cell shrinks because it loses its water and cell shrinking is called crenation or crinkling.
Isotonic condition
It means that the solute and solvent are equal. Hence, the net movement is equal and doesn't affect the cell much. This is known as the ideal condition for the animal cell.
In plant cell there are two conditions:
Hypotonic condition
It means to have more solvent and less solute. If a plant cell is placed in a hypotonic solution then the water from the surrounding (high concentration) travels inside the cell (lower concentration) through a partially permeable membrane. The cell swells up and becomes turgid because it has a rigid cell wall that bears the water pressure. If all the cells are turgid, then it stops the plant from wilting. Hence, this is known as the ideal condition for plant cells.
Hypertonic condition
It means to have less solvent and more solute. If a plant cell is placed in a hypertonic solution then the water from the cell(high concentration) travels to the surrounding (lower concentration) through a partially permeable membrane. The cell becomes flaccid in the first few minutes and then becomes plasmolyzed. In this condition the cytoplasm pulls away from the cell wall and the contents of the cell decrease in volume.
*picture taken from google*
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