what is the difference between osmosis and dialysis?

Answer 1

In both cases you have a semi-permeable membrane separating two solutions.

In the case of osmosis, solutes (which contribute to the phenomenon) cannot pass through the membrane and therefore the solvent has to pass through the membrane in order to equilibrate the osmotic pressure (or better yet the solvent potential) of the two solutions.

In the case of dialysis you have some solutes which can pass through the mebrane and diffuse from the solution where their concentration is higher to the one where their concentration is lower. Thus dialysis is used when you want to get rid of certain solutes or exchange them with others, while retaining some of the initial solutes in your system. E.g. if you have a protein sample that has too much salt, you can get rid of the salt (or any other small molecule that you don't want in your sample), without losing your protein, by dialysis; you can change the buffering system with dialysis. Of course there are also the medical aspects of dialysis but these have already been described in detail in the other answer.

In two words, in the case of osmosis you have net movement of solvent whereas in dialysis you have net movement of some solutes from one solution to the other.

Answer 2

1

Answer 3

osmosis-
transfer of a liquid solvent through a semipermeable membrane that does not allow dissolved solids (solutes) to pass

Dialysis- is a type of renal replacement therapy which is used to provide an artificial replacement for lost kidney function due to renal failure. It is a life support treatment and does not treat any kidney diseases. Dialysis may be used for very sick patients who have suddenly lost their kidney function (acute renal failure) or for quite stable patients who have permanently lost their kidney function

Answer 4

diffusion- random pass of molecules from one area of extreme concentration in the direction of certainly one of decrease concentration. dialysis-chemical technique that makes use of diffusion to chop up small molecules from greater ones in a liquid. (separation of solids from a liquid) osmosis-diffusion of water by way of a selectively permeable membrane in a reaction to a concentration gradient.

Answer 5

Treatment Reverse Chronic Kidney Problems - http://Kidney.NaturallyGo.com

Answer 6

Osmosis is the movement of water through a semipermeable membrane from a region of low solute potential to a region of high solute potential (or equivalently, from a region of high solvent potential to a region of low solvent potential). The semipermeable membrane must be permeable to the solvent, but not to the solute, resulting in a pressure gradient across the membrane. Osmosis is a natural phenomenon. However, it can be artificially opposed by increasing the pressure in the section of high solute concentration with respect to that in the low solute concentration. The force per unit area required to prevent the passage of solvent through a selectively-permeable membrane and into a solution of greater concentration is equivalent to the turgor pressure. Osmotic pressure is a colligative property, meaning that the property depends on the concentration of the solute but not on its identity.


Computer simulation of the process of OsmosisOsmosis is an important topic in biology because it provides the primary means by which water is
Consider a permeable membrane, such as visking tubing, with apertures small enough to allow water molecules, but not larger molecules, to pass through. Suppose the membrane is in a volume of pure water. At a molecular scale, every time a water molecule hits the membrane, it has a defined likelihood of passing through. In this case, since the circumstances on both sides of the membrane are equivalent, there is no net flow of water through it. However, if there is a solution on the other side, that side will have fewer water molecules and thus fewer collisions with the membrane. This will result in a net flow of water to the side with the solution. Assuming the membrane does not break, this net flow will slow and finally stop as the pressure on the solution side becomes such that the diffusion in each direction is equal. Osmosis can also be explained via the notion of entropy, from statistical mechanics. As above, suppose a permeable membrane separates equal amounts of pure solvent and a solution. Since a solution possesses more entropy than pure solvent, the second law of thermodynamics states that solvent molecules will flow into the solution until the entropy of the combined system is maximized. Notice that, as this happens, the solvent loses entropy while the solution gains entropy. Equilibrium, hence maximum entropy, is achieved when the entropy gradient becomes zero.

Examples of osmosis
Many plant cells perform osmosis. This is because the osmotic entry of water is opposed and eventually equaled by the pressure exerted by the cell wall, creating a steady state. In fact, osmotic pressure is the main cause of support in plant leaves.

When a plant cell is placed in a hypertonic solution, the water in the cells moves to an area higher in solute concentration, and the cell shrinks and so becomes flaccid [pron. flaxid]. (This means the cell has become plasmolysed - the cell membrane has completely left the cell wall due to lack of water pressure on it (the opposite of turgid)).

Osmosis can also be seen very effectively when potato slices are added to a high concentration of salt solution. The water from inside the potato moves to the salt solution, causing the potato to shrink and to lose its 'turgor pressure'. The more concentrated the salt solution, the bigger the difference in size and weight of the potato chip.

In unusual environments, osmosis can be very harmful to organisms. For example, freshwater and saltwater aquarium fish placed in water with a different salt level (than they are adapted to) will die quickly, and in the case of saltwater fish rather dramatically. Additionally, note the use of table salt to kill leeches and slugs.

In medicine, dialysis is a type of renal replacement therapy which is used to provide an artificial replacement for lost kidney function due to renal failure. It is a life support treatment and does not treat any kidney diseases. Dialysis may be used for very sick patients who have suddenly lost their kidney function (acute renal failure) or for quite stable patients who have permanently lost their kidney function (end stage renal failure). When healthy, the kidneys remove waste products (for example potassium, acid and urea) from the blood and also remove excess fluid in the form of urine. Dialysis treatments have to duplicate both of these functions as dialysis (waste removal) and ultrafiltration (fluid removal).

Dialysis works on the principle of the diffusion of solutes along a concentration gradient across a semipermeable membrane. In all types of dialysis, blood passes on one side of a semipermeable membrane, and a dialysis fluid is passed on the other side. By altering the composition of the dialysis fluid, the concentrations of undesired solutes (chiefly potassium and urea) in the fluid are low, but the desired solutes (for example sodium) are at their natural concentration found in healthy blood, or in the case of bicarbonate, greater, to neutralise the acidosis that is often present.

There are two main types of dialysis, hemodialysis and peritoneal dialysis. Hemofiltration is not strictly speaking a dialysis treatment, but is extremely similar.

In haemodialysis, the patient's blood is passed through a system of tubing (a dialysis circuit) via a machine to a semipermeable membrane (dialyzer) which has dialysis fluid running on the other side. The cleansed blood is then returned via the circuit back to the body. Ultrafiltration occurs by increasing the hydrostatic pressure of the blood in the dialysis circuit to cause water to cross the membrane down a pressure gradient. The dialysis process is very efficient, allowing the treatment to be undertaken intermittently, usually three times a week, but often fairly large volumes of fluid must be removed in a session which can sometimes be demanding on the patient.

In peritoneal dialysis, a special solution is run through a tube into the peritoneal cavity, the abdominal body cavity around the intestine, where the peritoneal membrane acts as a semipermeable membrane. The fluid is left there for a period of time to absorb waste products, and then is removed through the tube. This is usually repeated a number of times during the day. Ultrafiltration occurs via osmosis in this case, as the dialysis solution is supplied in varying osmotic strengths to allow for some control over the amount of fluid to be removed. The dialysis process in this case is less efficient than hemodialysis and is carried out daily, but the ultrafiltration process is slower and gentler.

Hemofiltration is a similar treatment to hemodialysis, but in this case, the membrane is far more porous and allows the passage of a much larger quantity of water and solutes to pass across it. The fluid which passes across the membrane (the filtrate) is discarded and the remaining blood in the circuit has its desired solutes and fluid volume replaced by the addition of a special hemofiltration fluid. It is a slow continuous therapy with sessions typically lasting 12-24 hours, usually daily. This, and the fact that ultrafiltration is very slow and thus gentle, makes it ideal for patients in intensive care units, where acute renal failure is common. A combination of hemofiltration and hemodialysis, called hemodiafiltration (incorporating a hemofilter to a standard hemodialysis circuit), is being used in some centres for chronic maintenance therapy.