What Is Tonicity In Cells
5.9: Passive Transport - Tonicity
- Folio ID
- 13090
- Define tonicity and describe its relevance to osmosis
Tonicity describes how an extracellular solution can change the volume of a cell past affecting osmosis. A solution's tonicity often directly correlates with the osmolarity of the solution. Osmolarity describes the total solute concentration of the solution. A solution with low osmolarity has a greater number of h2o molecules relative to the number of solute particles; a solution with high osmolarity has fewer water molecules with respect to solute particles. In a situation in which solutions of two different osmolarities are separated past a membrane permeable to water, though not to the solute, h2o will move from the side of the membrane with lower osmolarity (and more than water) to the side with higher osmolarity (and less water). This effect makes sense if you remember that the solute cannot move across the membrane, and thus the but component in the system that tin can move—the water—moves forth its own concentration gradient. An of import distinction that concerns living systems is that osmolarity measures the number of particles (which may exist molecules) in a solution. Therefore, a solution that is cloudy with cells may have a lower osmolarity than a solution that is clear if the second solution contains more dissolved molecules than in that location are cells.
Hypotonic Solutions
Three terms—hypotonic, isotonic, and hypertonic—are used to relate the osmolarity of a cell to the osmolarity of the extracellular fluid that contains the cells. In a hypotonic situation, the extracellular fluid has lower osmolarity than the fluid inside the cell, and water enters the prison cell. (In living systems, the point of reference is always the cytoplasm, so the prefix hypo- ways that the extracellular fluid has a lower concentration of solutes, or a lower osmolarity, than the cell cytoplasm. ) It as well ways that the extracellular fluid has a college concentration of h2o in the solution than does the cell. In this situation, water will follow its concentration slope and enter the prison cell, causing the cell to aggrandize.
Hypertonic Solutions
As for a hypertonic solution, the prefix hyper- refers to the extracellular fluid having a college osmolarity than the cell's cytoplasm; therefore, the fluid contains less water than the cell does. Because the cell has a relatively higher concentration of water, water will leave the cell, and the jail cell will shrink.
Isotonic Solutions
In an isotonic solution, the extracellular fluid has the aforementioned osmolarity every bit the prison cell. If the osmolarity of the cell matches that of the extracellular fluid, at that place will exist no cyberspace movement of water into or out of the jail cell, although h2o will yet move in and out.
Blood cells and plant cells in hypertonic, isotonic, and hypotonic solutions have on characteristic appearances. Cells in an isotonic solution retain their shape. Cells in a hypotonic solution swell as water enters the cell, and may burst if the concentration gradient is large enough between the within and outside of the cell. Cells in a hypertonic solution shrink every bit water exits the cell, condign shriveled.
Key Points
- Osmolarity describes the full solute concentration of a solution; solutions with a depression solute concentration have a low osmolarity, while those with a high osmolarity accept a loftier solute concentration.
- Water moves from the side of the membrane with lower osmolarity (and more than h2o) to the side with higher osmolarity (and less water).
- In a hypotonic solution, the extracellular fluid has a lower osmolarity than the fluid within the cell; h2o enters the prison cell.
- In a hypertonic solution, the extracellular fluid has a college osmolarity than the fluid inside the cell; h2o leaves the jail cell.
- In an isotonic solution, the extracellular fluid has the same osmolarity as the cell; there will exist no net movement of water into or out of the cell.
Key Terms
- osmolarity: The osmotic concentration of a solution, normally expressed as osmoles of solute per litre of solution.
- hypotonic: Having a lower osmotic force per unit area than some other; a cell in this surround causes water to enter the cell, causing information technology to swell.
- hypertonic: having a greater osmotic pressure than another
- isotonic: having the same osmotic force per unit area
What Is Tonicity In Cells,
Source: https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book:_General_Biology_%28Boundless%29/05:_Structure_and_Function_of_Plasma_Membranes/5.09:_Passive_Transport_-_Tonicity
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