In the process of dialysis, a special semipermeable membrane allows both small molecules and water to pass through, but not large protein molecules. These membranes are used to separate these small molecules and ions from much larger proteins. If a mixture of proteins and small molecules were separated from pure water by a dialysis membrane as shown in the figure, which way would the molecules flow?
A)Both water and small molecules would pass through into the pure water.
B)Only the proteins would pass through into the pure water.
C)Water would enter the solution while small molecules would pass through into the pure water.
D)Only small molecules would pass through the membrane; water and proteins would not.
E)Only water would pass through the membrane into the solution.

Question

In the process of dialysis, a special semipermeable membrane allows both small molecules and water to pass through, but not large protein molecules. These membranes are used to separate these small molecules and ions from much larger proteins. If a mixture of proteins and small molecules were separated from pure water by a dialysis membrane as shown in the figure, which way would the molecules flow? 
A)Both water and small molecules would pass through into the pure water. 
B)Only the proteins would pass through into the pure water. 
C)Water would enter the solution while small molecules would pass through into the pure water. 
D)Only small molecules would pass through the membrane; water and proteins would not. 
E)Only water would pass through the membrane into the solution.

Quizplus · Accepted Answer

Since the dialysis membrane is semipermeable and allows small molecules and water to pass through but not large molecules (such as proteins), the water would flow into the solution from the pure water side by a process known as osmosis. At the same time, small molecules would pass through the membrane into the pure water due to their smaller size. However, the proteins would be unable to cross the membrane and would remain on the other side. Therefore, only water would enter the solution while small molecules would pass through into the pure water.

In the Process of Dialysis, a Special Semipermeable Membrane Allows