Name
Class
Cell Transport Practice
Multiple Choice
Write the letter that best answers the question or completes the statement on the line provided.
__D___ 1. Which of the following is a function of the cell membrane?
a. breaks down lipids, carbohydrates, and proteins from foods
b. stores water, salt, proteins, and carbohydrates
c. keeps the cell wall in place
d. regulates the movement of materials into and out of the cell
___D__ 2. The cell membrane contains channels and pumps that help move materials from one side to
the other. What are these channels and pumps made of?
a. carbohydrates
c. bilipids
b. lipids
d. proteins
___B__ 3. Diffusion occurs because
a. molecules are attracted to one another.
b. molecules constantly move and collide with each other.
c. cellular energy forces molecules to collide with each other.
d. cellular energy pumps molecules across the cell membrane.
___A__ 4. An animal cell that is surrounded by fresh water will burst because the osmotic pressure
causes
a. water to move into the cell.
c. solutes to move into the cell.
b. water to move out of the cell.
d. solutes to move out of the cell.
Completion
Complete each statement on the line provided.
5. ____Cholesterol____________________ helps strengthen the lipid bilayer.
6. A protein imbedded in the cell membrane with a carbohydrate chain attached
_glycoprotein______________.
7. ____Integral_____________ proteins span the entire width of the membrane and could function as
carrier or channel proteins.
Short Answer (2pts ea.)
8. What advantages do cell walls provide plant cells that contact fresh water?
Cell walls allow the plant cell to swell with water from the exterior environment without
bursting. The tough and flexible cell wall made of cellulose can withstand the osmotic
pressure.
9. Explain, in terms of osmosis, why a raisin placed in a cup of pure water overnight will puff up with
water.
The raisin in has been placed in a hypotonic environment. More water is surrounding the raisin
than is inside the raisin therefore the water moves from high concentration outside the raisin to
low concentration inside the raisin causing to puff up.
Use the diagram below to answer the following questions on the lines provided. (2pts ea.)
A student put together the experimental setup shown below. The selectively permeable membrane is
permeable to water, but not the solute shown.
Figure 7–4
10. Describe the experimental setup shown in Figure 7–4.
A selectively permeable (semi permeable) membrane divides a vessel in half. Different amounts
of solute and water are on either side of the membrane. The membrane is not permeable to the solute.
______________________________________________________________________________
11. How does the solution on Side A of the apparatus shown in Figure 7–4 differ from the solution on
Side B?
On side A the solution has a higher concentration of water because there is less solute.
12. Look at Figure 7–4. Describe the movement of water in the experimental setup. What will happen
to the concentration of water over time?
Water will move from side A to side B. Eventually the water will reach equilibrium with both
side A and B having equal amount of water.
13. Which side of the experimental setup is hypertonic to the other?
Side B has a higher solute concentration that side A, so side B is hypertonic to A.
14. Once equilibrium is reached in the apparatus shown in Figure 7–4, will the water molecules
continue to move? Explain your answer.
The water molecules will continue to move back and forth across the membrane at equal rates.
After equilibrium is reached the water is not trapped on either side but continues to be exchanged
equally from side to side.
Essay
Write the answer to each question in the space provided.
15. Our current representation of the cell membrane’s structure is often referred to as a fluid mosaic
model. Explain how the cell membrane relates to a fluid and a mosaic. (5pts)
The cell membrane is like a fluid because it is flexible, able to repair itself when disturbed (polarity of
phospholipids re-orient), and parts that make up the cell membrane like phospholipids and proteins can
move laterally with the membrane itself.
The membrane is like a mosaic because it is made individual phospholipids, proteins, carbohydrates,
and cholesterol. The assembly of all these parts forms the overall structure of the membrane similar to
how individual tiles in a mosaic form a pattern or picture.
16. Construct a diagram of the phospholipid bilayer. Include a total of 4 phospholipids. Be sure to
label the heads and tails, identify polar and nonpolar regions, and hydrophobic/hydrophilic
regions.(5pts)
Hydrophilic
Hydrophilic
17. Explain why water must use an aquaporin to pass through the cell membrane.(4pts)
An aquaporin must be used for water to enter and exit the cell because water is polar. The polarity of
water causes it to be rejected by the non-polar region of the lipid bilayer. The non-polar region of the
bilayer is in the middle of the membrane and is comprised of the non-polar tails. The aquaporin is an
integral channel protein that is hydrophilic and allows water to pass through the membrane avoiding
the non-polar region of the bilayer.