you are working with a novel cell that is eprmeable to nacl but impermeable to u

Question

you are working with a novel cell that is eprmeable to nacl but impermeable to urea. look at the table of solutions on table 1. in you manual. consider solution 2, 4 And 9. determine the osmolarity and tonicity for these solutions in light of the fact that nacl is penetration and urea is non penetrating, explain your reasoning for each scenario.

2- 33mM NaCl, osmolarity is 66 and observed tonicity is hypo

4-150mM nac, osmolarity is 300 and observed tonicity is iso

9-300 mM urea, osmolarity is 300 and observed tonicity is hypo

Explanation / Answer

Osmosis and tonocity are quite similar. The difference is only about of the pressure gradient.

osmosis: is a case of diffusion that involves the passive movement of water. And water(solvent) move from high to low concentrations through a semipermeable membrane.

Tonocity: is the measure of the osmotic pressure gradient of two solutions seprated by the membrane. There are three conditions : Hypotonic, Hypertonic, isotonic.

So we are working on a novel cell that is permeable to Nacl but impermeable to urea.

In solution 2. 33mm Nacl is taken the osmolality is 66mmmol (because nacl dissociate into two particles)so:

33mmol×2= 66mmol.

The predicted observation was hypertonic but the observed tonocity comes hypotonic. Because solution has high concentration of solute due to dissociation of nacl and water enter into the novel cell due to which it become turgid and condition is hypotonic.

Solution no.4:-150mm nacl osmolality is 300mmol . The predicted tonocity was iso.and the observed tonocity is also isotonic . This is because the osmolality of nacl in blood is approx to 300mmol. An isotonic solution has same solute content as another solution . That is why the 150mmmol is isotonic

Solution no. 9. Here the 300mmol urea solutions is taken .the osmolalrity is 300mmol. The predicted tonocity was 300 but observed was hypotonic solution. Because urea solution when enter into novel cell down its concentration gradient due to which conc. Of solute will increase and conc. Of solvent will decrease due to which water move into the cell. And the tonocity is hypotonic.

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