Download Diffusion, Osmosis, and Cell Membranes

Name:______________________________________________ Period:________
(Answer the following questions on the back of this sheet or your own paper)
Movement Across Membranes
I. Define the following terms:
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Diffusion
Osmosis
Equilibrium
Semipermeable membrane
Passive transport
Active transport
II. Suppose that you have an osmosis apparatus like the one that you used in the diagram
below. In one side of the apparatus, there are a 100 mL of solution composed of distilled
water and iodine. In the other side, there is a 10% starch solution. The cell membrane is
permeable to iodine and water, but is not permeable to starch. The liquid levels in both
sides are initially the same. Answer the following questions in complete sentences.
a. What will happen to the level of the water and iodine solution (Side A)?
b. What will happen to the level of the starch solution (Side B)?
c. In which direction across the semipermeable membrane will the water molecules move when the system
reaches equilibrium?
d. What will happen to the color of the water and iodine solution? Why?
e. What will happen to the color of the starch solution? Why?
f. How many grams of starch will be present in 100 grams of the 10% starch solution?
III. Often when a person is ill they must be given fluids intravenously (by injection
directly into the blood vessel). Why must the person never be given pure water
intravenously? Be sure to explain your answer in full, using the concepts of diffusion
and osmosis that we have discussed.
Name:______________________________________________ Period:________
(Answer the following questions on the back of this sheet or your own paper)
IV. Choose A.)Active Transport or B.)Passive Transport for each of the following.
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Large molecules enter or leave the cell by this method
Small molecules enter or leave the cell by this method
Involves moving from an area of high to low concentration
Involves moving from an area of low to high concentration
Requires energy
Requires no energy
Involves the use of protein pumps
Osmosis falls into this category
Another word for this type of transport is diffusion
An uncharged molecule would use this method
V. Evaluate the following diagram and answer the questions that follow:
Solute molecule
Water molecule
Is the cell surrounded by a hypertonic or hypotonic solution? How do you know?
In which direction will water flow? Why?
Eventually, what will happen to this cell?
If the cell were isotonic with its surrounding solution, what would happen to the size of
the cell? Why?
VI. Describe the difference between voltage gated ion channels and carrier proteins embedded
within the cell membrane.