Exploring Biology Topics can reveal the incredible complexity and interconnectedness of living systems.
Diffusion of Plasma Membrane
Some substances (molecules, ions) such as carbon dioxide (CO2), oxygen (O2), water, etc., can move across the plasma membrane through a process called diffusion. These substances are of very small size, so, they diffuse readily through the phospholipid layer of the plasma membrane. To understand this process let us perform Activity.
Let us take a glass beaker or a glass tumbler half filled with clean water. Put a few drops of blue ink or any coloured fluid into the beaker or tumbler. What do you observe? Does the water in the beaker or tumbler gets uniformly coloured throughout at once?
You will observe that the ink diffuses into the water gradually until the ink molecules get uniformly distributed in the water. This is a spontaneous movement of a substance from a region of a high concentration to a region where its concentration is low.
Representation of diffusion which is the movement of molecules or ions from an area of higher concentration to the region of lower concentration.
Thus, diffusion is the spontaneous movement of molecules from a region of high concentration to one of lower concentration, until uniform concentration is finally achieved. Diffusion is faster in the gaseous phase than in liquids and solids.
Something similar to the diffusion of ink in Activity happens in cells when for example, a gas such as CO2 gets accumulated in high concentration inside a cell. In the external environment of the cell, the concentration of CO2 is low as compared to the inside of the cell. As soon as there is a difference in concentration of CO2, inside and outside of a cell, CO2 moves out of the cell, i.e., from the region of its high concentration to the region of low concentration by the process of diffusion. In a similar way, oxygen (O2) enters the cell (e.g., Amoeba) by the process of diffusion when the level or concentration of O2 inside the cell decreases.