Question

1. The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal.

a.which side will have a higher final volume?
b. What will diffuse first across the membrane and in what direction? (Think about these molecules and their sizes.)
c.In terms of tonicity, are the sides initially hypertonic, isotonic, or hypotonic? Explain your answer.
d.In what direction will water move across the membrane?

Answer 1

a. Side B will have a higher final volume because water will move from Side A to Side B until the concentration of water is equal on both sides.

b. Glucose will diffuse first from Side B to Side A because there is a higher concentration of glucose in Side B. Sucrose will not diffuse at all because it cannot pass through the membrane.

c. Both sides are initially isotonic because the concentration of solutes (sucrose and glucose) is equal on both sides.

d. Water will move from Side A to Side B because Side B has a higher concentration of solutes (sucrose and glucose) and therefore a lower concentration of water. This movement of water will continue until the concentrations of solutes and water are equal on both sides.