Tag: Osmosis definition
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Osmosis: Definition, Mechanism, and Examples
Continue ReadingWhat is Osmosis?
The net flow of solvent molecules through a semipermeable membrane is referred to as osmosis. It’s comparable to diffusion in that it moves downhill, from a higher to a lower concentration. However, in osmosis, the movement must take place over a semipermeable barrier.Â
Osmosis cannot be called osmosis without this component. While diffusion refers to the net movement of solutes between two solutions, osmosis is concerned with the net movement of solvent molecules, such as water molecules. The difference in water molecule concentration between the two sides of the membrane is what causes the water to migrate in order to bring the concentrations of the two sections closer together.
Osmosis Definition
Osmosis is defined in biology as the net transfer of water molecules from a higher to a lower water potential area through a semipermeable membrane (e.g., the cell membrane).
Other osmosis definitions are as follows:
1. The process of a solvent diffusing from a low-solute-concentration area to a high-solute-concentration area via a semipermeable barrier.
2. The ability of water to flow through a semipermeable barrier from a hypotonic solution (low concentration of dissolved chemicals) to a hypertonic solution (high concentration of dissolved substances).
Osmosis is characterized similarly in chemistry. When two solutions are separated by a membrane that selectively inhibits the passage of solute molecules while allowing the passage of solvent molecules. It is the passage of a pure solvent from one with a lower concentration of solutes to another with a higher concentration of solutes.
Osmosis Etymology
The word osmosis is a Latinized version of the now-defunct osmose. Osmotic is a derived word that means “pertaining to or of the character of osmosis.” Osmotic pressure, for example, is a pressure that occurs as a result of osmosis.
How Osmosis Works?
(1) net downhill flow of water molecules, (2) a selectively permeable membrane, and (3) an osmotic gradient are all required for osmosis to occur. Water molecules tend to migrate downhill, from a high-water concentration (or fewer solutes) to a low water concentration (or vice versa) (or greater solutes).
It cannot be considered osmosis if there is no net flow of water. It should also include a semipermeable barrier to allow for movement. Without it, the process is only diffusion rather than osmosis. Because water molecules are polar, channel proteins are required for them to travel along their concentration gradient.
These channel proteins are implanted in the cell membrane and create a hydrophilic conduit for water to flow through. The osmotic (pressure) gradient, or the difference in osmotic pressures between the two solutions, is what causes the water molecules to migrate.
Water potential is a measurement of the relative tendency of water to migrate from one location to another. The Greek letter Ψ is often used to symbolise it (Psi). Different tonicities of solutions produce a net flow of water across the cell membrane.
A solution consists mostly of the solute (material to be dissolved) and the solvent (the component that dissolves the solutes). The concentrations of components in two solutions will decide whether one is isotonic, hypotonic, or hypertonic in comparison to another.
Isotonic Solution
An isotonic solution is one in which the number of solutes in one solution is about equal to the number of solutes in another solution. A cell that is isotonic to the outside solution, for example, indicates that the internal fluid and the outside fluid have the same osmotic pressure and water potential. There will be no net flow of water molecules between the cell and the surrounding fluid in this instance.
Hypotonic Solution
A hypotonic solution is one that has a lower osmotic pressure (or contains fewer solutes) than the solution it is compared to. To dilute the solution, water flows toward the area with less water concentration or towards the more concentrated portion. Water will flow across the membrane and into the cell’s more concentrated solution if the fluid around the cell is hypotonic, for example.
Hypertonic Solution
A hypertonic solution is one that appears to be the polar opposite of a hypotonic solution. In comparison to the other solutions, a hypertonic solution contains more solutes and less water. Water will exit a cell submerged in a hypertonic solution to dilute the solution outside.
Osmosis Examples
i. Osmosis in Animal Cells
Osmosis is important in biological systems because many biological membranes are semipermeable, and it has a variety of physiological consequences. When animal cells are exposed to a hypertonic (lower water concentration) environment, the water leaves the cells, causing the cells to shrink. Crenation is the medical term for this ailment. When animal cells are put in a hypotonic environment (i.e., one with greater water content), water molecules migrate into the cells, causing them to expand. Cells will eventually rupture if osmosis persists and becomes extreme.
ii. Osmosis in Plant Cells
Plant cells do not rupture owing to an excessive amount of water input. Plants use their cell walls and vacuoles to protect themselves against excessive osmosis. The plant cell is stabilised by osmotic pressure exerted by the cell wall. Osmotic pressure, in fact, is what keeps plants upright. The big vacuole inside the plant cell aids osmoregulation, a regulatory process in which water potential is controlled to keep the osmotic pressure inside the cell within the optimal range.
Water efflux, on the other hand, does not protect plant cells. When a plant cell is put in a hypertonic environment, the cell wall is unable to prevent water loss. Cells shrink or become flaccid as a result of this.
Osmosis Citations
- Reverse osmosis desalination: water sources, technology, and today’s challenges. Water Res . 2009 May;43(9):2317-48.
- Brackish water desalination using reverse osmosis and capacitive deionization at the water-energy nexus. Water Res . 2020 Sep 15;183:116064.
- Emerging thin-film nanocomposite (TFN) membranes for reverse osmosis: A review. Water Res . 2020 Apr 15;173:115557.
- Forward osmosis membrane technology for nutrient removal/recovery from wastewater: Recent advances, proposed designs, and future directions. Chemosphere . 2021 Jan;263:128116.
- Forward osmosis membrane processes for wastewater bioremediation: Research needs. Bioresour Technol . 2019 Oct;290:121795.
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Osmosis: Definition, Mechanism, and Examples
Continue ReadingWhat is Osmosis?
The movement of water molecules across semi permeable membrane to produce a homeostatic system in cell and its environment is the process of osmosis.
Characteristic of Osmosis
Osmosis was derived from Latin which means impulse or urge; of the solvent to move uphill from lower concentration to higher concentration. The main difference between osmosis in living and non – living cells are the properties of the particular system. Osmosis in non – living cells can be demonstrated by separating the solution and water by a semipermeable membrane.
Osmosis is a type of diffusion between a solution and water when separated by a biological membrane which is permeable for solvents and restrict the entry of solutes.
Fick’s law can be theoretically applied to the diffusion where the rate of diffusion is directly proportional to the concentration gradient and area over the diffusion occurs. Experiments are done to depict the mechanism of osmosis in a living tissue where a solution and pure solvent present in two chambers A and B separated by a semi permeable membrane and observed from the initial time T. After a particular time say T’ to maintain a system equilibrium and restrain by the membrane the pure solvent enters the chamber A of solution to maintain the equilibrium. As the pure solvent enters Chamber A increasing volume of the chamber indicating the movement of the solvent from lower to higher concentration.
Osmosis Examples
Water is transported by vascular tissues xylem where the nonliving tracheid are also taking up the water. In leaves mesophyll cells; the tracheid’s opens to the cells and water enters cell via Osmosis. Semipermeable part of the cells is the plasma membrane. Plasma membrane along with cellular components are protoplast. The liquid part is called as the protoplasm and other cellular components (i.e.) organelles are also separated from each other by membranes. Plant cells are specialized by carrying a vacuole and cell wall both has its specific role in plants structure.
Additionally; plasma membrane is protective and regulative in nature by the mechanism of osmosis and presence of channels and transmembrane which transports particulate compounds for cellular metabolism. Further the plant is surrounded by Rigid Cell Wall which provides a particular shape for the cell.
Vacuoles – storage part of the cells stores nutrients and water in turn maintaining the internal volume of the cell. Externally the cells are connected by rigid cellulose made cell wall mediating communication between each other cells. Inside the cell wall they are separated from other cells by intercellular spaces.
Principle of Osmosis
Osmosis works on a basic principle of chemical potential difference between 2 components separated by a semi permeable membrane. Chemical potential is the free energy available per mole of the substance in a solution. In the osmosis demonstration the pure solvent had high energy compared to the solution which had lower energy (i.e.) lower chemical potential which created a gradient to pure solvent enter the Chamber A. The potential difference arises because of the solute in the cytoplasm which are part of energy metabolic activities constantly replenishes the chemical molecules and are dynamic in nature.
Semi permeable membrane does not allow solute molecules and solute or ion uptake is mediated by ATP utilizing carrier proteins knows as active transport breaking down ATP to produce energy for ion uptake. Active transport of ions constitutes a potential difference between an internal and external environment develops a chemical potential gradient taking up water molecules from xylem. This indicates for every active uptake of ion generates a potential difference involves a passive entry of water into the cell and thereby osmosis is indirectly coupled with energy utilization.
Osmosis is Pressure Dependent
Similar experiments can be quoted to prove the pressure during osmosis. Osmotic pressure is the maximal amount of pressure developed in a system separated by a semipermeable membrane by pure water. Pressure due to osmosis is demonstrated using an osmometer; where a thistle funnel is inverted and covered with a semipermeable membrane is separated by solution A and B; where A is pure solvent and B is solution. At time T’ osmosis happens and the volume of Solution B increases.
On attaching a piston and maintaining the same volume in osmometer by producing a pressure through a piston maintains volume constant for a particular time and when the pressure in piston is increased the water flow reverses from Solution A to Solution B. The pressure of the osmosis is directly dependent on the solute concentration. Dependent on solute concentration makes the process a colligative property of a solution along with 3 other properties.
Osmosis and Turgor Pressure
Turgor pressure or the phenomenon of turgidity is maintained by the process of osmosis; involves vacuoles, protoplast wherein the water uptake in vacuole produces a basic crispness in cell structure and additionally the protoplasm as a whole requires water to maintain rigidity of plant cell thereby making the whole plant stand erect. When a cell loses its water content the leaves and stem wilts and the state is flaccid and prolonged flaccid nature of plants leads to death. To retain the structure water uptake becomes essential which is mediated by osmosis.
Importance of Osmosis
• Partially; the water uptake from soils controlled by osmosis in roots.
• Facilitate water movement from non – living part to the living part of the plant.
• Mechanical support of rigidity is provided by osmosis.
• A special ability of osmosis allows a plant to be turgid and helps in movement of ions in plants.
• Osmotic pressure produces a growth in plants.
• Opening and closing of stomata, flower is done with the help of osmosis.
Osmosis Citations
- Forward osmosis membrane technology for nutrient removal/recovery from wastewater: Recent advances, proposed designs, and future directions. Chemosphere . 2021 Jan;263:128116.
- Forward osmosis membrane processes for wastewater bioremediation: Research needs. Bioresour Technol . 2019 Oct;290:121795.
- Measuring osmosis and hemolysis of red blood cells. Adv Physiol Educ . 2017 Jun 1;41(2):298-305.
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