Question

11. Each of the dialysis tubes was labeled "10%". What does that mean?

Answer 1

Answer: 11. 10% is the concentration of solutes, 12. Osmosis is the net movement of solvent through a membrane according to the concentration of the solution.

Explanation:

Osmosis is a phenomenon that explains the movement of a solvent through a semi-permeable membrane without expenditure of energy, where the movement is through simple diffusion.

The tonicity is the total concentration of all solutes in the solution. Then, when a solution has a few particles, it has a low osmolarity, while a solution with many particles has a hight osmolarity. But, when there are two solutions separated by a permeable membrane to water (and not to the solutes or particles) the solvent (water) will move from the lower osmolarity side to the higher osmolarity side (which means, water moves from a region of low concentration to a region of high concentration)

To compare osmolarity of solutions, we use the terms hypertonic, hypotonic and isotonic. This is done, for example, to compar the osmolarity of a cell with the osmolarity of the extracellular fluid around it.  If the extracellular fluid has a lower concentration than the fluid inside the cell, it is hypotonic with respect to the cell. In this case, the solvent will go into the cell.  If the extracellular fluid has a higher concentration than the fluid inside the cell, it is hypertonic and the solvent will leave the cell from the region of lower solute concentration to the region with more solutes. At last, an isotonic solution is when the extracellular fluid and the cell has the same osmolarity and there will be no net movement of water in or out of the cell.

Increasing on mass would mean that there has been a net movement of water into the bag, because the solution was hypotonic. A decreased on mass mean that there has been a net movement of water out of the bad, because the solution was hypertonic. And if there has been no change or a very little mass change, it means the solution was isotonic, the same osmolarity or concentration of solutes was found inside and outside the cell.

Taking into account the concepts of tonicity and osmolarity, we can explain the process of dialysis which is the process of separating molecules across a semi-permeable membrane in a solution by the difference in their osmotic pressure. It is a laboratory technique where a solution that has many types of different solutes, is put into a semi-permeable sealed dialysis bag, (such as a porous cellulose membrane). Then it is placed in a container with a different solution, or pure water (which has a lower osmolarity). Molecules such as DNA or proteins are larger than the diameter of the pore thereby they are retained within the dialysis bag. However, molecules that are small enough to pass through the pores, such as water, tend to move in or out of the dialysis bag in the direction of the lowest concentration. It is usually used to remove salt from a protein solution.  Then, if a dyalisis tube is labeled as 10%, it means its solute concentration is 10% of to the total volume of the dialysis bag.