What Determines Tonicity?

How is tonicity determined?

“Whereas a solution's osmolarity is based solely on its total solute concentration, its tonicity is determined by how it affects cell volume, which depends not only on the solute concentration but also on the solute permeability of cell membranes. A solution is said to be isotonic when it does not alter cell volume.

What contributes to tonicity?

Tonicity is a measure of the relative concentration of solute particles on either side of a semi-permeable membrane (e.g. inside a cell versus outside the cell). Only solutes that cannot cross the membrane contribute to tonicity. It determines the direction and extent to which water moves by osmosis.

What determines the tonicity of a solution relative to a cell?

The tonicity of a solution is related to its effect on the volume of a cell. Solutions that do not change the volume of a cell are said to be isotonic. A hypotonic solution causes a cell to swell, whereas a hypertonic solution causes a cell to shrink.

Related Question What determines tonicity?

What are the methods of adjusting tonicity?

Tonicity equivalent or sodium chloride equivalent method is used to adjust the tonicity of pharmaceutical solutions. Sodium chloride equivalent (E) of a drug is the amount of sodium chloride that is equivalent to 1 gm of the drug.

Does glucose contribute to tonicity?

Tonicity depends only on the concentration of nonpenetrating solutes, so any solution of pure glucose will be hypotonic, no matter what its osmolarity, and tonicity describes only the change in cell volume at equilibrium.

How does tonicity affect animal cells?

The effects of Tonicity by means of different solutions are given below: Effect on living animal cells: The animal cells, such as red blood cells, will become crenated. When placed in a hypertonic solution, their appearance will consist of an irregular surface (water moves external to the cell).

How do you compare the tonicity of a solution?

If a solution has a higher concentration of solutes (less water) than another it is said to be hypertonic. A hypotonic solution has a lower concentration of solutes and more water than another solution. Isotonic solutions contain the same concentration of solutes.

How does tonicity affect osmosis?

Tonicity describes how an extracellular solution can change the volume of a cell by affecting osmosis. A solution with low osmolarity has a greater number of water molecules relative to the number of solute particles; a solution with high osmolarity has fewer water molecules with respect to solute particles.

What tonicity causes osmosis?

What causes Crenation of red blood cells?

When red blood cells are in a hypertonic (higher concentration) solution, water flows out of the cell faster than it comes in. This results in crenation (shriveling) of the blood cell.

What is the tonicity of the extracellular fluid?

Tonicity describes how an extracellular solution can change the volume of a cell by affecting osmosis. A solution's tonicity often directly correlates with the osmolarity of the solution. Osmolarity describes the total solute concentration of the solution.

Why is tonicity important in clinical practice?

Having a good understanding of tonicity gives a good insight into how dehydration can affect the cells of the body. An isotonic solution is best because the osmotic pressure within and outside the cell is equal, so there is no net movement of water and the cells will retain their shape and function.

How do solutes affect tonicity?

Tonicity depends on the relative concentration of selectively membrane permeable solutes across a cell membrane which determine the direction and extent of osmotic flux. Unlike osmotic pressure, tonicity is influenced only by solutes that cannot cross the membrane, as only these exert an effective osmotic pressure.

Which of the following adjusts tonicity of ophthalmic?

Sodium nitrate should be used to adjust the tonicity and phenylmercuric nitrate can be used as the preservative in this situation.

Which ion is used as tonicity agent?

The USP 29-NF 24 lists five excipients classified as "tonicity" agents, including dextrose^(1,2), glycerin^(1,3), mannitol^(1,4), potassium chloride^(1,5) and sodium chloride^(1,6).

How does osmolarity differ from tonicity?

Osmolarity and tonicity are related but distinct concepts. The terms are different because osmolarity takes into account the total concentration of penetrating solutes and non-penetrating solutes, whereas tonicity takes into account the total concentration of non-freely penetrating solutes only.

How does dextrose affect tonicity?

For example, 5% dextrose, when infused, is iso-osmolar with the body fluid compartments. Its osmolality is the same as the osmolality of the cellular contents (about 300mOsm/L) However, because dextrose penetrates the cells so easily, it cannot contribute to tonicity.

Why is tonicity relevant in IV fluids?

In this context, the tonicity rather than the volume of the IV fluid is relevant, as this hypertonic solution will attract water from the intracellular compartment. As such, hypertonic saline can be used to treat cerebral edema in hyponatremic encephalopathy.

How does tonicity relate to the direction of water movement across a membrane?

When solutions of different osmolarities are separated by a membrane permeable to water, but not to solute, water will move from the side with lower osmolarity to the side with higher osmolarity. If two solutions have the same osmolarity, they are said to be isoosmotic.

What is tonicity in biology?

Tonicity is defined as the ability of a solution surrounding a cell to cause that cell to gain or lose water (Urry et al., 2017). While osmolarity is an absolute quantity, tonicity is relative. If two solutions have the same concentration of nonpenetrating solutes, they are considered isotonic.

What tonicity of a solution is preferred by animal cells?

Animal cells tend to do best in an isotonic environment, plant cells tend to do best in a hypotonic environment.

What is tonicity in biology quizlet?

Tonicity. A description of the relative solute concentration in a solution as compared to another solution. Equilibrium. The condition that exists in system when there is a relatively equal distribution of a particular molecule. Hypertonic.

What is the difference between osmosis and tonicity?

Osmosis describes the number of solutes dissolved in a volume of solution. It has units whereas tonicity has no units. Osmolarity is comparing two solutions. Tonicity is comparing a solution and a cell.

How is tonicity related to osmolarity?

Tonicity is equal to the osmolality less the concentration of these ineffective solutes and provides the correct value to use. Osmolality is a property of a particular solution and is independent of any membrane. Tonicity is a property of a solution in reference to a particular membrane.

What is crenation process?

In biology, crenation describes the formation of abnormal notched surfaces on cells as a result of water loss through osmosis. The cells start to shrivel and form abnormal spikes and notches on the cell membrane. This process is called crenation.

What is the significance of crenation?

A process resulting from osmosis in which red blood cells, in a hypertonic solution, undergo shrinkage and acquire a notched or scalloped surface. A process resulting from osmosis in which red blood cells, in a hypertonic solution, undergo shrinkage and acquire a notched or scalloped surface.

What tonicity causes Plasmolysis of plant cells?

Plasmolysis is the process in which cells lose water in a hypertonic solution. The reverse process, deplasmolysis or cytolysis, can occur if the cell is in a hypotonic solution resulting in a lower external osmotic pressure and a net flow of water into the cell.

What is tonicity in biochemistry?

Tonicity. Tonicity is the capability of a solution to modify the volume of cells by altering their water content. The movement of water into a cell can lead to hypotonicity or hypertonicity when water moves out of the cell.

Why is tonicity important in pharmacy?

It is important for a solution to be isotonic with a bodily fluid to prevent irritation and cell damage, and to maximise drug efficacy.

Why is sodium chloride used as a tonicity agent?

Sodium chloride has uses a channeling agent, and as an osmotic agent in the cores of controlled-release tablets. It also is used to help modify drug release, and to adjust porosity in tablet coatings. Sodium chloride is widely used in a variety of pharmaceutical products to produce isotonic solutions.

What are the reasons for adjusting and buffering the pH of an ophthalmic preparation?

Buffers are needed to stabilize the pH at a level at which drugs are soluble, active, and tolerable. Because buffer capacity is regulated by its concentration, some formulations use higher dosages to enhance the drug's performance.

Which method of adjusting Isotonicity is a modified White Vincent method?

The Sprowls method, a modified method of the White–Vincent method, calculates the isotonic volume by using fixed mass of the material. The milliequivalent method is similar to the NaCl equivalent method in which the ingredient mixture must be equal to 0.9% of NaCl content in mEq/L.

What cells need this tonicity to be at homeostasis?

Animal cells need to be in isotonic solutions to be at homeostasis. Homeostasis is a balance and is important for all living things to maintain.