Hypertonic,+hypotonic+and+isotonic+effects+on+plants+and+animal+cells.

=**Hypertonic, Isotonic and Hypotonic Solutions and How They Effect Plant and Animal Cells. - Becky Hitchen**=

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**Introduction to tonicity**
**Tonicity** is a measure of effective osmolarity in cell biology. Osmolarity is the properties of a particular solution, **independent of any membrane**. Tonicity is a property of a solution in **reference to a particular membrane**, and is equal to the sum of the concentrations of the solutes which have the capacity to exert an osmotic force across that membrane. Tonicity, also, depends on solute permeability **(permeant solutes do not affect tonicity; impermeant solutes do affect tonicity).** Tonicity is generally classified in three ranges; **hyper tonicity, hypo tonicity and isotonicity**. Hypertonic, isotonic and hypotonic solutions are defined in reference to a cell membrane by comparing the tonicity of the solution with the tonicity within the cell.

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The word "HYPER" means more, so hypertonicity refers to a solution that has a higher or more of a concentration to it's external environment. The cell has a higher number of particles (solutes) dissolved in it than the solution outside of the cell membrane. When a cell’s cytoplasm is bathed in a hypertonic solution the water will be drawn into the solution and out of the cell by osmosis. This causes water to move out of the cell, it shrivels up and shrinks.=====

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In animal cells, being in a hypertonic environment results in **crenation**, where the shape of the cell becomes distorted and wrinkled as water leaves the cell. Some organisms have evolved methods of venting Hypertonicity; for example, saltwater is hypertonic to the fish that live in it. Since they cannot isolate themselves from osmotic water loss, because they need a large surface area in their gills for gas exchange, they respond by drinking large amounts of water, and excreting the salt. This process is called osmoregulation. An example of an animal cell showing the affects of hypertonicity is when your fingers wrinkle.===== Figure 2; Hypertonicity (source; http://imcurious.wikispaces.com/Midterm+Exam+2010+Review+P1 ) Figure; 3 wrinkled fingers (reaction to hypertonicity) (source; [|www.healthfitnessguru.com/water/questions]

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When a plant cell is placed in a hypertonic solution, the water inside the cells are drawn out by osmosis. The vacuoles decrease in size. The cytoplasm also shrinks away from the cellulose cell wall and **plasmolysis** occurs. This causes a lack of structure for the plant and causes it to wilt, or become flaccid.=====

Figure; 4 Hypertonic in plants (source; [|www.spmbiology403.blogspot.com] ) Figure; 5 Wilting plant (hypertonic reaction) (source; [|www.dontkillu2live.wordpress.com] )

**Hypotonic**
The word "**HYPO**" means less, in this case there are less solute molecules outside the cell. Cells hypotonic to their surrounding solutions cause water to move into the cell and cause it to expand. The cell has a smaller number of solutes than the solution outside of the cell membrane. A hypotonic solution is a solution having a lesser solute concentration than the cytosol. It contains a lesser concentration of impermeable solutes on the external side of the membrane. When a cell’s cytoplasm is bathed in a hypotonic solution the water will be drawn out of the solution and into the cell by osmosis. If water molecules continue to diffuse into the cell, it will cause the cell to swell, up to the point that cytolysis (rupture) may occur. The opposite of a hypertonic environment is a hypotonic one, where the net movement of water is into the cell. If the cell contains more impermeable solute than its surroundings, water will enter it.

**HOW IT AFFECTS ANIMAL CELLS;**
In an animal cell, hypotonic solutions cause them to swell, they become bloated and triple their original size. By the time they have reached triple their size (how long this takes depends on each individual cell) they burst like a balloon and die.

Figure; 6 Hypotonic (source; [|www.spmbiology403.blogspot.com] ) Figure; 7 Blood cells having a hypotonic reaction (source; [|www.proprofs.com] )

**HOW IT AFFECTS PLANT CELLS;**
When plants are placed in water, the water enters their cells (this is because their sap has a strong solution). The water enters the plant through osmosis and fills up the cell with water to its maximum capacity. A strong cell wall stops the cells from bursting (as in animal cells) and makes the plant to become turgid (becomes rigid/stiff because of water.)

Figure 8; Hypotonic in plant cells (source;
[] ) Figure 9; Turgid Plant (source; [|www.cactus-art.biz] )

**Isotonic**
A cell in an isotonic environment is **in a state of equilibrium** with its surroundings. When the amount of impermeable solute is the same on the inside and outside of the cell, osmotic pressure becomes equal; the force of water trying to exit and enter the cell balances out."**ISO**" means the same meaning that the osmotic pressure and concentration of solutes is the same in both the internal and external environments of the cell. Cells isotonic to their surrounding solutions have an equal concentration of solutes in and out of the cell membrane. This creates a dynamic equilibrium that maintains the status of the cell. **No change will occur in the cell.**