Question #76
A system is constructed such that two solutions are separated by a semi-permeable membrane. On side A is placed 1 L of water in which 100 mmol sucrose and 100 mmol fructose are dissolved. On side B is placed 2 L of water in which 200 mmol sucrose and 200 mmol fructose are dissolved. The membrane is permeable to fructose and water only. Which of the following combinations of hydrostatic pressures exerted by an external source on sides A and B of the membrane respectively will result in its remaining undeformed?
The membrane is permeable to frustose and this is therefore an ineffective osmolyte.
Sucrose, the only effective osmolyte, is present at equal concentrations on both sides of the membrane. At equilibrium there is, therefore, no net osmotic pressure acting to deform the membrane. If it is to remain undeformed then no net hydrostatic pressure can be exerted. Of the options presented the situation where a hydrostatic pressure of 100 cmH2O is exerted on both sides of the membrane is thus the only one that will not in itself lead to deformation.
See A Thinking Approach to Physiology
, pages 177 - 179.