<< Chapter < Page Chapter >> Page >

Hypertonic solutions

As for a hypertonic    solution, the prefix hyper - refers to the extracellular fluid having a higher 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.

Isotonic solutions

In an isotonic    solution, the extracellular fluid has the same osmolarity as the cell. If the osmolarity of the cell matches that of the extracellular fluid, there will be no net movement of water into or out of the cell, although water will still move in and out. Blood cells and plant cells in hypertonic, isotonic, and hypotonic solutions take on characteristic appearances ( [link] ).

Art connection

The left part of this illustration shows shriveled red blood cells bathed in a hypertonic solution. The middle part shows healthy red blood cells bathed in an isotonic solution, and the right part shows bloated red blood cells bathed in a hypotonic solution.
Osmotic pressure changes the shape of red blood cells in hypertonic, isotonic, and hypotonic solutions. (credit: Mariana Ruiz Villareal)

A doctor injects a patient with what the doctor thinks is an isotonic saline solution. The patient dies, and an autopsy reveals that many red blood cells have been destroyed. Do you think the solution the doctor injected was really isotonic?

For a video illustrating the process of diffusion in solutions, visit this site .

Tonicity in living systems

In a hypotonic environment, water enters a cell, and the cell swells. In an isotonic condition, the relative concentrations of solute and solvent are equal on both sides of the membrane. There is no net water movement; therefore, there is no change in the size of the cell. In a hypertonic solution, water leaves a cell and the cell shrinks. If either the hypo- or hyper- condition goes to excess, the cell’s functions become compromised, and the cell may be destroyed.

A red blood cell will burst, or lyse, when it swells beyond the plasma membrane’s capability to expand. Remember, the membrane resembles a mosaic, with discrete spaces between the molecules composing it. If the cell swells, and the spaces between the lipids and proteins become too large, the cell will break apart.

In contrast, when excessive amounts of water leave a red blood cell, the cell shrinks, or crenates. This has the effect of concentrating the solutes left in the cell, making the cytosol denser and interfering with diffusion within the cell. The cell’s ability to function will be compromised and may also result in the death of the cell.

Various living things have ways of controlling the effects of osmosis—a mechanism called osmoregulation. Some organisms, such as plants, fungi, bacteria, and some protists, have cell walls that surround the plasma membrane and prevent cell lysis in a hypotonic solution. The plasma membrane can only expand to the limit of the cell wall, so the cell will not lyse. In fact, the cytoplasm in plants is always slightly hypertonic to the cellular environment, and water will always enter a cell if water is available. This inflow of water produces turgor pressure, which stiffens the cell walls of the plant ( [link] ). In nonwoody plants, turgor pressure supports the plant. Conversly, if the plant is not watered, the extracellular fluid will become hypertonic, causing water to leave the cell. In this condition, the cell does not shrink because the cell wall is not flexible. However, the cell membrane detaches from the wall and constricts the cytoplasm. This is called plasmolysis    . Plants lose turgor pressure in this condition and wilt ( [link] ).

Questions & Answers

Simple term of science
Palesa Reply
what does it mean
it's means what do u know about biology?
what is immunisation
what is the biology? what do you know about biology
Phathu Reply
biology is the study of living organisms, divided into many specialized fields that cover their morphology, physiology, anatomy, behavior, origin, and distribution.
The study of all aspects of life. The study of all living organisms (such as animal cells and plant cells) in greater detail (their structure and how they function). It's a very broad science.
what is prokaryotic
Bhaskar Reply
what is pathogens
transistion metals....
Wasik Reply
Why study ecology
Amos Reply
What name is given to group 8metals on a periodic table
what is evolution
Elia Reply
Is the gradual change of something it can be either organisms
which of the following statements about the moss life cycle is false?
Israel Reply
posterior lobe of pitutary contains what?
MR Reply
What if vincristine and colchicibe disrupt mitosis by binding to tubulin
Rohith Reply
A plant in the understory of a forest displays a segmented stem and slender leaves arranged in a whorl. It is probably....
Israel Reply
How did the development of a vascular system contribute to the increase in size of plants?
If a flower lacked a megasporangium and microsporangium, what type of gametes would not form?
Seed plants are.. A. all homosporous B. mostly homosporous with some heterosporous C. mostly heterosporous with some homosporous D. all heterosporous
Besides the seed, what other major structure diminishes a plant's reliance on water for reproduction?
what role did the adaptations of seed and pollen play in the development and expansion of seed plants?
Some cycads are considered endangered species and their trade is severely restricted. Customs officials stop suspected smugglers who claim that the plants in their possession are palm trees, not cycads. How would a botanist distinguish between the two types of plants?
What are the two structures that allow angiosperms to be the dominant form of plant life in most terrestrial ecosystems?
how are carbohydrates,proteins and fats formed from triose phosphate
fonyuy Reply
Why does the actin filament only move in one direction? Describe in great detail.
Lashonda Reply
Two events happen when calcium binds to troponin.
which of the following statements about plant division is false?
Israel Reply
😂😂😂 i dont know how i reached here
What are the events that occur in each phase of interphase
Hazey Reply
what is photosynthesis
Victor Reply
The process plants use to convert sunlight into food (energy).
Some other organisms use
types of photosynthesis
ps1 and ps2

Get the best Biology course in your pocket!

Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Biology' conversation and receive update notifications?