<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Define osmosis and explain its role within molecules
  • Explain why osmoregulation and osmotic balance are important body functions
  • Describe active transport mechanisms
  • Explain osmolarity and the way in which it is measured
  • Describe osmoregulators or osmoconformers and how these tools allow animals to adapt to different environments

Osmosis is the diffusion of water across a membrane in response to osmotic pressure    caused by an imbalance of molecules on either side of the membrane. Osmoregulation is the process of maintenance of salt and water balance ( osmotic balance    ) across membranes within the body’s fluids, which are composed of water, plus electrolytes and non-electrolytes. An electrolyte    is a solute that dissociates into ions when dissolved in water. A non-electrolyte    , in contrast, doesn’t dissociate into ions during water dissolution. Both electrolytes and non-electrolytes contribute to the osmotic balance. The body’s fluids include blood plasma, the cytosol within cells, and interstitial fluid, the fluid that exists in the spaces between cells and tissues of the body. The membranes of the body (such as the pleural, serous, and cell membranes) are semi-permeable membranes . Semi-permeable membranes are permeable (or permissive) to certain types of solutes and water. Solutions on two sides of a semi-permeable membrane tend to equalize in solute concentration by movement of solutes and/or water across the membrane. As seen in [link] , a cell placed in water tends to swell due to gain of water from the hypotonic or “low salt” environment. A cell placed in a solution with higher salt concentration, on the other hand, tends to make the membrane shrivel up due to loss of water into the hypertonic or “high salt” environment. Isotonic cells have an equal concentration of solutes inside and outside the cell; this equalizes the osmotic pressure on either side of the cell membrane which is a semi-permeable membrane.

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. One of the bloated cells in the hypotonic solution bursts.
Cells placed in a hypertonic environment tend to shrink due to loss of water. In a hypotonic environment, cells tend to swell due to intake of water. The blood maintains an isotonic environment so that cells neither shrink nor swell. (credit: Mariana Ruiz Villareal)

The body does not exist in isolation. There is a constant input of water and electrolytes into the system. While osmoregulation is achieved across membranes within the body, excess electrolytes and wastes are transported to the kidneys and excreted, helping to maintain osmotic balance.

Need for osmoregulation

Biological systems constantly interact and exchange water and nutrients with the environment by way of consumption of food and water and through excretion in the form of sweat, urine, and feces. Without a mechanism to regulate osmotic pressure, or when a disease damages this mechanism, there is a tendency to accumulate toxic waste and water, which can have dire consequences.

Mammalian systems have evolved to regulate not only the overall osmotic pressure across membranes, but also specific concentrations of important electrolytes in the three major fluid compartments: blood plasma, extracellular fluid, and intracellular fluid. Since osmotic pressure is regulated by the movement of water across membranes, the volume of the fluid compartments can also change temporarily. Because blood plasma is one of the fluid components, osmotic pressures have a direct bearing on blood pressure.

Questions & Answers

Parkinson's disease is a caused by the degeneration of neurons that release
birabwa Reply
why is it so hard to get to the questions
Eric Reply
why is it so hard to get to questions?
Eric
what types of proteins which are found in hair,hooves and tendons?
Kapalu Reply
what is blood cells
Isaac Reply
It's cells of the blood
Kaique
can biology be also be define has a scientific study that deal with life?
Stanley Reply
do you care asking you a question
Afolayan Reply
name the gas that diffuses into the plants leaves on a bright, sunny day
Tuhemwe Reply
explain why this gas diffuses into the plant's leaves
Tuhemwe
name two gases that diffuses out of the plant's leaves on a bright sunny day
Tuhemwe
Biology olympaid
Khan
what is ecosystem
Rondy Reply
why does a car move yet it is not a living thing?
Sserujja
this is because of the engine and fuel placed on
Gift
I also think it because force has been apply to it.
Stanley
It is aplace where organísms live and associate with each other.
Nasib
what is the reason of swelling due to fracture
Ejaz Reply
Sngy alaka
Khan
how do animals reproduce
Kelvin Reply
be specific because there are so many types of animals and how they reproduce are different
Sheillah
yeah
Chinwendu
just be specific with a particular animal
Stanley
what happens when you sneeze
Asuquo Reply
The sneeze center sends out a signal to tightly close your throat, eyes and mouth. Your chest muscles contract and compress your lungs while your throat muscles relax. All of that means air, saliva and mucus is forced out of your nose and mouth. AAAAAHHHH-CHOOOO.
Hassan
how are you
Ayouba
hy
Ejaz
hii
Ishitha
hello
mahesha
Hello
Madu
Am fine
Abavon
how far
Abavon
hello
Sheillah
with why
Sheillah
with what
Sheillah
I have a question plzz
Sheillah
what is globsl warming
Rondy
Global warming is the overall rise in temperature of the Earth itself which is caused by multiple factors. Such factors include: greenhouse gases, the burning of fossil fuels and other forms of human activity.
Maryam
It's overall effects are known as climate change.
Maryam
thanks
Rondy
good
Haider
No problem.
Maryam
Thank you.
Maryam
what is creatinine?
Haider
Creatinine is a waste product produced in the body during muscle metabolism. This waste product is expelled from the body through urine. Here is it's formula:  C4H7N3O
Maryam
Formula: C4H7N3O
Maryam
ok
Haider
ok
Stephen
Outline the process of cell in the body interms of it's function.
Aliruku Reply
what communication method used mainly by plants
Jerda Reply
what is biology
james Reply
Biology is the study of life
Omoloju
yah
John
Biology is natural science that studies life and living orgasms.
Hilda
any questions from colleague
Sheillah
define nerve impulse
Karlin Reply
A nerve impulse is the way nerve cells (neurons) communicate with one another. Nerve impulsesare mostly electrical signals along the dendrites to produce a nerve impulse or action potential. The action potential is the result of ions moving in and out of the cell.
Sam

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?

Ask