Osmosis: Definition, Types, Osmotic Pressure, Examples, & Facts

Osmosis is the movement of water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration. It is a crucial biological process that helps maintain cell turgidity and regulates fluid balance in living organisms. In this article, osmosis, basic principles of osmosis, mechanism of osmosis, osmotic pressure, types of solutions in osmosis, biological significance of osmosis, and applications of osmosis are discussed. Osmosis is a topic of the chapter Transport in Plants in Biology.

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This Story also Contains

1. What is Osmosis?
2. Basic Principles of Osmosis
3. Mechanism of Osmosis
4. Osmotic Pressure
5. Types of Solutions in Osmosis
6. Biological Significance of Osmosis
7. Applications of Osmosis

What is Osmosis?

Osmosis is the flow of water molecules across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. Such processes and similar ones in biological systems support the maintenance of cellular turgor pressure, nutrient uptake, waste removal, and generally cellular activity and homeostasis.

Basic Principles of Osmosis

Osmosis is one of the most basic concepts in biology, closely related to but distinct from diffusion since it deals with the movement of water across a semipermeable membrane.

Diffusion and Osmosis

• The flow of particles from an area of higher concentration to an area of lower concentration is described as diffusion.

• Osmosis refers to the flow of water molecules through a semipermeable membrane caused by concentration differences.

Semipermeable membrane

• A membrane that some molecules, mainly water, pass through while others are blocked.

• Biological Examples: The cell membrane, the membranes of mitochondria and chloroplasts.

Also Read-

• MCQ Practice on Osmosis
• Transport in Plants
• Reverse Osmosis
• Diffusion

Mechanism of Osmosis

The mechanism of osmosis is of great importance to the maintenance of cellular balance and function. This is the passive movement of water molecules.

Water Molecules Movement

• Concentration Gradient: Water moves from low to high concentration.

• Direction of Water Movement: Water moves into areas with high concentrations of solutes.

• This process tends to equilibrate the solute concentration inside and outside the cell.

Osmotic Pressure

• The pressure must be applied to just prevent the transfer of water across a semipermeable membrane.

• Factors Affecting Osmotic Pressure: Solute concentration, temperature, and the properties of the membrane.

Osmotic Pressure

The pressure needed to prevent water from osmotically diffusing over a membrane is known as osmotic pressure. It is based on the solute's concentration. From the area of lower concentration, water diffuses into the area of higher concentration. The compounds will disperse until the concentration is consistent throughout when the concentrations of the substances in the two places in contact are different.

Osmotic pressure can be calculated using the equation:

Π=MRT

where Π denotes the osmotic pressure,

M is the molar concentration of the solute,

R is the gas constant,

T is the temperature

Types of Solutions in Osmosis

Osmosis can occur in different kinds of solutions. These have different effects on cells.

Hypotonic Solutions

• A solution with a low solute concentration compared to that of the cell's interior.

• Causes cells to swell and potentially burst due to the entrance of water.

Hypertonic Solutions

• A solution with a higher solute concentration than that of the cell's interior.

• Cause cells to shrink as water exits.

Isotonic Solutions

• A solution with the same solute concentration as that of the cell's interior.

• No net movement of water, the cell stays the same size and shape.

Biological Significance of Osmosis

Osmosis is involved in many biological processes, mainly in plant and animal cells.

Plant Cells

• Turgor Pressure: The pressure exerted by the cell's content against the cell wall, maintaining rigidity and the form of plants.

• Plasmolysis and Its Effects: Due to the hypertonic solution, the plant cells lose water, detaching the cell membrane from the cell wall, which may even cause the death of the cell.

Animal Cells

• Osmoregulation: The process by which animals maintain the proper balance of water and salts within their bodies.

• Effects of Osmosis on Red Blood Cells: The effects of osmosis on red blood cells can be such that they may burst in a hypotonic solution and shrink in a hypertonic solution.

Applications of Osmosis

Osmosis is involved in various medical and industrial applications.

Medical Applications

• Dialysis: A medical procedure in which waste products and excess water are removed from blood through the principle of osmosis when the kidneys are no longer functioning.

• Intravenous Fluids: Solutions given to patients to maintain osmotic balance and hydration.

Industrial Applications

• Food Preservation: Osmotic pressure to prevent growth/spoiling by microorganisms.

• Water Purification: Reverse osmosis, for instance, to purify water from impurities and contaminants.

Also Read-

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