Diffusion – Means of Transport

By definition, the process of diffusion implies the movement of molecular level substances or particles from the region of higher concentration to a region of lower concentration. It is also described as a passive form of transportation. A passive form of transportation implies that the objects in motion do not contribute to their movement. Diffusion is a natural and physical process, which happens on its own without the need for any form of energy. The occurrence of diffusion happens over liquids and gases as the molecules can move randomly. The molecules collide with each other and change the direction thus forming a passive form of transport.

The diffusion of substances in the atmosphere is one of the most common phenomena in the environment. For example, a perfume when sprayed disperses the molecules into the air. Here, the perfume bottle holds the substance at a higher concentration. When the air is dispensed from the bottle, the substance diffuses into the atmosphere as the atmosphere is of a lower concentration when compared to the bottle. The process of diffusion enables the perfume’s odor to propagate throughout the area.

Diffusion also acts as a means of transport in ecological life. For example, plants grow and survive by consuming water, minerals and utilize them to create their food by using a process called photosynthesis. The water and minerals are extracted by the roots and leaves are responsible for preparing the food. The food is then transported to the other parts of the plant. The logistics or the transportation of these raw ingredients are handled by the process of diffusion. Diffusion is an important process as not only does it transport raw materials from the roots to the leaves and food to other parts of the plants but also, during the process called transpiration, the water and oxygen diffuse from the leaves into the environment.

Factors Affecting Diffusion

The process of diffusion is comparatively very slow and occurs mostly in gases and liquids. This passive form of transportation does not utilize any form of energy. However, the rate of diffusion depends on various factors like the ones listed below:

Pressure/Concentration Gradient
Size of the particles
Temperature
Density

The pressure gradient is defined as the ratio between the high and the low concentration regions. It is directly proportional to the rate of diffusion. The size of the particles also affects the rate of diffusion. The smaller the size, the faster is the diffusion rate. The temperature facilitates in increasing the rate of diffusion as it can increase the pressure. The density however does not facilitate in increasing the rate of diffusion and thus is inversely proportional to the rate of diffusion.

Types of Diffusion

The transportation of particles by using the process of diffusion can happen using two methods namely,

Simple Diffusion
Facilitated Diffusion

Simple Diffusion implies the movement of particles from one concentration to another without having to combine the particles with any constituents that aids in the increase of diffusion rate. The rate of diffusion is relatively slower than the facilitated diffusion.

Facilitated Diffusion is the movement of particles from one concentration to another by aiding in the process of diffusion. It is also a selective process, i.e., the membrane only allows a certain type of molecule to pass through and prevents the other molecules from entering. This is important as facilitated diffusion ensures that the plants are capable of segregating different minerals from the soil through the roots. The rate of diffusion is faster than the simple diffusion. However, this form of diffusion can be either passive or active depending on the type of carrier assisting in the diffusion.