2. As a relative concentration of solutes in two solutions increases, of necessity the concentration of water in
the same two solutions INCREASES. Solution A has a lower concentration of SOLUTE than does Solution C;
Solution A is also hypertonic to Solution C.
3. If you wanted to make Solution A isotonic to Solution B, you could add water to Solution B or you could
add solute to Solution A. If you took all three solutions, put them into a large container and mixed them
thoroughly, then redistributed the solution among three containers, Solution A would be ISOTONIC to
Solution B. Solution A would also be ISOTONIC to Solution C, and Solution C would be ISOTONIC to
Solution B.
Part III – Look at the solutions and cells illustrated above and fill in the blanks.
1. Because the cytoplasms of the plant and the animal cell have equal concentrations of solutes, we can say
their cytoplasms are ISOTONIC to each other. If we put both the plant and the animal cells into Solution A,
we would expect no change in the cells, because Solution A is ISOTONIC to the cytoplasm of each cell.
2. Let’s put both cells into Solution B. Because Solution B is hypertonic to the cytoplasms of the cells, we
would expect water to LEAVE the cells through the process of OSMOSIS. This would result in the cytoplasm
of both cells shrinking.
3. Now we’ll put both the plant and animal cell into Solution C, which, because it contains no solutes at all, is
HYPOTONIC to the cytoplasm of both cells. WATER will enter both cells through osmosis. The animal cell is
likely to BURST, unfortunately. The plant cell, however, is protected from this because of the presence of its
CELL WALL.
Refer to the U-tube pictures above when answering the questions below.
1. Why did the number of water molecules on each side of the membrane change, whereas the number of
sugar molecules stayed the same? WATER MOLECULES ARE SMALL ENOUGH TO PASS THROUGH THE
PORES OF THE MEMBRANE, HOWEVER, THE SUGAR MOLECULES ARE NOT.
2. How does the plasma membrane of a cell compare with the membrane in the U-shaped tube?
THEY ARE BOTH SELECTIVELY PERMEABLE BASED ON SIZE OF PARTICLES