Types of Passive Transport

Passive transport is mainly categorised into four types based on how the molecules move across a membrane. These are:

Simple Diffusion

In simple diffusion, molecules move on their own without any support along the concentration gradient. Particles move from a highly crowded region to a less crowded area. This movement occurs till the point an equilibrium is established. E.g. The exchange of oxygen and carbon dioxide in the lungs occurs with the help of diffusion.

Facilitated Diffusion

Facilitated diffusion is defined as the substances moving through the semi-permeable membrane from a region of higher concentration to a region of lower concentration with the help of transport proteins. These proteins form channels or carriers to allow the passage of the molecules. This movement is faster as compared to simple diffusion. E.g The movement of water molecules through the body occurs with the help of channel proteins known as aquaporins.

Osmosis

Osmosis is a type of facilitated diffusion that happens on the basis of water potential. In this, water moves from a region of low solute concentration to a region of high solute concentration across a semi-permeable membrane. The semi-permeable is selective in nature and allows only specific molecules to pass through it and blocks the others. Osmosis can be further divided into two types based on the direction of the movement of water. If the water moves towards the inside of the cell, the process is known as Endosmosis. If the water moves outside the cell, then the process is known as Exosmosis.

Filtration

Filtration involves the process of separation of solids from liquids and gases. This also does not involve the use of energy and works according to the concentration gradient. The membrane utilised for this process is selective in nature which allows soluble substances to pass through and stops the other molecules. E.g. In humans, the kidneys are responsible for the filtration process. The kidneys allow the body to absorb useful nutrients and water and the rest of waste material is excreted from the body.

Also Read: Filtration

Passive transport is one of the techniques used for transportation in plants and animals. Transport usually occurs in two forms- Active transport and Passive transport. Active transport helps in the uphill movement of substances. On the other hand, passive transport helps in the downward movement of substances. There are four types of passive transport- diffusion, facilitated diffusion, osmosis, and filtration. In this article, we will study the definition of passive transport, types of passive transport, diagram, of passive transport, examples of passive transport, the difference between active transport and passive transport, and the importance of active transport.