Download Osmosis WS

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Date
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CRITICAL THINKING: OSMOSIS
Part 1. The direction in which water molecules move during osmosis depends on where the water are
more highly concentrated. Study the diagrams below. Decide whether the solution in each beaker is
hypotonic, isotonic, or hypertonic in relation to the solution inside the cell. Draw arrows to indicate the
direction in which the water will move in each case.
A
1.
80% H2O
20 % glucose
100% H2O
0% glucose
90% H2O
10% glucose
90% H2O
10% glucose
80% H2O
20% glucose
90% H2O
10% glucose
B
C
Intravenous solutions must be prepared so that they are isotonic to red blood cells. A 0.9 percent
salt solution is isotonic to red blood cells.
a. Explain what will happen to a red blood cell placed in a solution of 99.3 percent water and 0.7
percent salt.
b. What will happen to a red blood cell placed in a solution of 90 percent water and 10 percent
salt? Explain.
Part 2. During a lab, three lengths of dialysis tubing were filled with a 2.0 M sucrose solution. A knot
was then tied in the other end so that as much air as possible was excluded. The tubes were then rinsed
in distilled water. The tubes were weighed and one tube each was placed in the following solutions.
 Solution A: 4.0 M sucrose
 Solution B: 2.0 M sucrose
 Solution C: distilled water
At 15 minute intervals the sacs were removed weighed. The data/graphs are shown.
1.
Which
a.
b.
c.
solution is…
isotonic to the solution in the dialysis tube?
hypotonic to the solution in the dialysis tube?
hypertonic to the solution in the dialysis tube?
2. In regard to the solutions in the bags and in the beakers, what
is meant by equilibrium?
3. What happens to the motion of molecules after equilibrium is
reached?
Part 3. Slide 1 is an onion in an isotonic solution. Note the position and shape of the cell wall, cytoplasm
and vacuole. Slide 2 is an onion section which has had a 10% NaCl solution added. You will find that the
cytoplasm has shrunk away from the cell wall. The cell is said to be plasmolyzed.
Slide 1
Slide 2
1.
What happens to the water that was inside the cell?
2. What two characteristics of cell membrane are necessary in order for osmosis to occur?
3. Why wouldn't the cell burst if placed in distilled water, as an animal's cell would?
4. How is osmotic pressure important in the normal structure of a plant?
5. How does being placed in a hypertonic solution affect a plant?
6. What is turgor pressure in a plant cell?
Part 4. Fill in the missing words.
Type of Solution
______________ - water will
move into a cell
_____________ – water
moves in and out of the cell at
equal rates
_____________– water will
move out of the cell
Plant Cell
Animal Cell