Difference between Osmosis and dialysis

Difference between osmosis and dialysis


The difference between osmosis and dialysis is that Osmosis is a physical phenomenon by which a solvent passes through a semi-permeable membrane without implying an energy expenditure. The dialysis is a process for separating molecules present in a solution using a semipermeable membrane, employing the difference between their rates of diffusion.

What is Osmosis?

It is a physical phenomenon in which a solvent and part of the solute move through a semi-permeable membrane. This process allows a simple diffusion through the said membrane without thereby incurring an energy expenditure. In simple words, if we have two mixtures of water and some solute, with different concentrations of solute and we separate them with a semi-permeable membrane, the water, and the diluted solute will pass into the mixture with a lower concentration of solute until both solutions have the same concentration.

What is a semi-permeable membrane? It is a structure with small holes or porosities of reduced size. They only allow the passage of small molecules. Osmosis occurs when this membrane separates two solutions with a different concentration of molecules each. At this point, the solvent chemical molecules or particles will pass through the membrane until the chemical potentials on both sides of the membrane are balanced. In osmosis, solvent molecules pass through the semi-permeable membrane from the solution with a lower concentration of solute, called a hypotonic solution, to the one with a higher concentration, known as a hypertonic solution. Water osmosis is an important biological phenomenon in the metabolism of living beings. It occurs in cells and other membranes and is vital for our survival.

What is Dialysis?

It is the movement of colloidal particles suspended in a solvent, according to their different diffusion rates, when they are forced to cross a semi-permeable membrane. It is a process in which colloidal particles are separated according to their size through a semi-permeable or dialyzer membrane. This membrane only allows the passage of molecules of a certain size and water and prevents colloidal particles and macromolecules from passing through.

For example, if you have a mixture of water and different solutes and you want to do a dialysis process, you must place said mixture in a semi-permeable bag, then submerge it in a container with a different solution or pure water. The smallest molecules will pass through the pores into the solution in the bag and into the solution in the container, always in the direction of the solution with the lowest concentration. Larger molecules will remain in the dialysis bag. It is a common technique in laboratories and in medicine, where it is used to remove toxins and excess water from the blood. Dialysis is a renal replacement therapy that replaces kidney function when it is lost.

Before summarizing the differences between these two processes, we recommend that you consult the following links, where you will find a video explanation and extra information to enrich the concepts that we have presented:

Difference between Osmosis and Dialysis in points

  • Osmosis is a process through which a solvent passes through a semi-permeable membrane from an area with a lower concentration to an area with a higher concentration of solute.
  • Osmosis occurs inside cells, they absorb and diffuse nutrients and water, passing them through a semi-permeable membrane.
  • Dialysis is a medical process used to replace the filtering functions of the kidneys when the kidneys cannot work. Blood and a dialysate fluid are passed separated by a semi-permeable membrane. The toxins pass through the membrane into the dialysate solution to reach equilibrium. That is, they go from an area with a higher concentration of solute to one with a lower concentration.
  • Dialysis in biochemistry is a process that separates molecules from a solution thanks to the difference in their diffusion rates by forcing it to pass through a semi-permeable membrane.
  • In diffusion, the solute particles dissolve homogeneously in the solvent.
  • In dialysis we find a process of separation of a colloidal solute, that is, it is a solute that does NOT dissolve in the solvent.

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