What is Osmosis

Jean-Antoine Nollet made the basic observation of osmosis in the year 1748. The term “osmosis” originates from the “words” “exosmose” and “endosmose”. Osmosis is a process in which a fluid passes through semi permeable membrane. The movement of solvent molecules occurs from the region of lower concentration to a region of higher concentration.

Basic Principle

The primary motive of such a process is to equalize concentration of the solute on both sides of the selectively permeable membrane. It needs to be borne in mind that the selectively permeable membrane is leaky to the solvent but not to the solute. Osmosis is the physical movement of any solvent without the input of energy. The process of osmosis makes use of kinetic energy to carry out the entire movement of the solvent. The primary motive of osmosis is to create an “isotonic” state. Isotonic state is defined as the state in which there is an equal amount of fluid on either side of the barrier.

Two Main Factors

The factors of osmosis are listed below.

  • Osmotic Gradient
  • Osmotic Pressure

Osmotic pressure of a solution can be defined as force per unit area required to prevent passage of water across a selectively permeable membrane. Osmotic pressure intends to restrict the movement to the solution of greater concentration. Osmotic pressure is primarily a colligative property implying that the property depends upon the concentration of the solute rather than the identity of the solute. The difference in concentration between the two solutions is termed as the osmotic gradient. The difference in concentration exists across either sides of the semi-permeable membrane.

Variation of Osmosis

Primarily, there exist two main types of osmosis. The variation of osmosis is highlighted below:

  • Forward Osmosis
  • Reverse Osmosis

One needs to realize the fact that forward osmosis is an area of ongoing research. Forward osmosis primarily focuses on areas including water purification, food processing, desalination, and water treatment.

Reverse Osmosis

Reverse osmosis is primarily a separation process that makes use of pressure to force solvent through semi-permeable membrane. Reverse osmosis primarily aims to force the solvent from an area of higher concentration to an area of low solute concentration. The applied pressure is higher with respect to the osmotic pressure. One of the best examples of osmosis is when plants use osmosis for absorbing nutrients and water from soil. The roots of the plants act as selectively permeable membranes allowing the entry of water along with other essential minerals as well.

Osmosis bears paramount importance in the biological systems as well. It is a fact that osmosis plays a significant role in existence of plants and animals. Osmosis allows the entry fluids, essential nutrient, and the exit of waste products. Osmosis is the primary means by which water is transported in and out of the cells of living organisms.