Name: ___________
Plasma Membrane and Cellular Transport
Remedial Assignment
(Just for the record … the preferred method of completing and turning in this assignment is
to “save as” to your own directory, answer (in another colour) on computer and then send
me the .doc via email (rstevenson@papcs.com) Of course, you could always print it up and turn
in but hey, a few less trees murdered seems better to me. If any of this is confusing see me
about it)
PLASMA MEMBRANE & CELLULAR TRANSPORT

A semipermeable membrane that regulates interactions of the cell and its surroundings covers
each cell. Functions include separating the cell from its outside environment, controlling which
molecules enter and leave the cell, and recognizing chemical signals.

Passive and active transport contribute to homeostasis. The processes of diffusion and active
transport are important in the movement of materials in and out of cells.
Structure of the Plasma Membrane
Structure of the Plasma Membrane
Now load the CyberEd Biology Course Title: The Plasma Membrane
and Cellular Transport. View scenes 1 –5 and complete the exercise
below.
Multimedia
Presentation
View the structural components and their role in the plasma
membrane.
Scene 1
1. Why do you think it is important to have a membrane surrounding each of our trillions of cells?
Expect varying answers, but the idea is have the students understand the plasma membrane separates
the cells from their environment and each other while also regulating the material within each cell.
Scene 2 - 3
2. What are two distinctive physical features of phospholipids?
Heads are polar (water soluble, hydrophilic) and (water insoluble,
hydrophobic).
3. Describe the conformation of the phospholipid bilayer of the plasma membrane. What abundant
fluid leads to this conformation?
Because the phospholipids heads water.
Scene 4
4. How does the plasma membrane demonstrate its fluid nature of the Fluid Mosaic Model? What
molecule in the plasma membrane directly affects the membrane’s fluidity?
The phospholipids of
5. How does the plasma membrane demonstrate its mosaic nature of the Fluid Mosaic Model?
Protein molecules are embedded within the phospholipid
Scene 5
6. What is the function of the glycoproteins and glycolipids of the plasma membrane?
serve as cellular identifiers or signatures. They help the cell recognize friend and foe.
7. Use the illustration to identify the following components of the plasma membrane: cholesterol,
glycoprotein, phospholipids, membrane protein, and glycolipid.
A. Glycoprotein
B.
C. Membrane protein
D. Cholesterol
E.
Structures of the Plasma Membrane
Please load the CyberEd Biology Course Title: The Plasma
Membrane and Cellular Transport. Complete Interactive Lessons # 1.
Practice identifying the structures of the plasma membrane.
Interactive
Lesson
Cellular Transport: Diffusion and Osmosis
Cellular Transport: Diffusion and Osmosis
Now load the CyberEd Biology Course Title: The Plasma Membrane
and Cellular Transport. View scenes 6 - 19 and complete the exercise
below.
Multimedia
Presentation
Learn about the movement of molecules along a concentration gradient
in solutions.
Scene 6
1. Define cellular homeostasis. How does the plasma membrane contribute to cellular homeostasis?
Cellular homeostasis is the maintenance of a constant environment within a cell, in which the plasma
membrane regulates the passage of molecules across it.
Scene 8
2. Describe the movement Scottish scientist Robert Brown observed
in the suspended pollen grains. What causes the pollen to move in
such a way and what is this motion now known as?
Brown observed the constant jittery movements of pollen grains
suspended in water. The motion of pollen grains was a result of the
random motion and collision of molecules, now known as Brownian
motion.
Scene 9
3. Define diffusion.
Diffusion is the movement of particles from a region of high concentration to a region of lower
concentration.
Scene 10
4. What is the concentration gradient?
The concentration gradient is a difference in concentration between a region of higher concentration and
region of lower concentration.
5. Use the graphics (A and B) to answer the following questions on diffusion.
5a. The moving food coloring particles in Glass A demonstrate
what molecular process?
Diffusion
5b. What conditions must exist in Glass A for this movement to
occur?
There must be a concentration gradient, a difference in
concentration between the food coloring and the water.
5c. In Glass B, what is the concentration difference between food coloring and
water?
None
5d. When the concentration of food coloring and water in Glass B reach this
balance, what is this state called?
Dynamic equilibrium
Scene 11
6. The cell continually produces carbon dioxide as a by-product of cellular respiration. How does the cell
keep carbon dioxide from building up in the cytoplasm and poisoning the cell?
Carbon dioxide diffuses across the plasma membrane into the where its concentration is lower than in the
cell.
Scene 12
7. What distinguishes osmosis from diffusion?
Osmosis is the diffusion of water, whereas diffusion can be applied to any molecule.
Scenes 13 – 14
8. If the concentration of protein in one solution (Solution A) is greater than a second solution (Solution
B), in which solution is the concentration of water greater?
The second solution (Solution B)
9. Use the illustration to answer the following questions about osmosis.
9a. In which direction will water move
through the membrane? If the proteins
could diffuse, in which direction would they
move?
Water will move from B to A. Proteins
would diffuse from A to B, if they could.
9b. Osmotic pressure is the pressure
exerted by water on its container as it moves
by osmosis into a region of lower water
concentration. What do you think might
happen if a pressure equivalent to osmotic
pressure was applied to side A?
The water would not move from side B t
Scene 15 – 19
10. Fill in the summary tables for each type of solutions.
10a. What is an isotonic solution?
The concentration of dissolved substances is equal inside the cytoplasm and in the extracellular fluid.
Inside the cell
Concentration of dissolved substances
Equal
Concentration of water
Equal
Membrane
Isotonic Solution
Outside the cell
Equal
Equal
What happens to an animal cells?
Dynamic Equilibrium
What happens to a plant cell?
Dynamic Equilibrium
10b. What is a hypotonic solution?
The concentration of dissolved substances is less in fluid than in the cytoplasm.
Inside the cell
Concentration of dissolved substances
Greater
Concentration of water
What happens to an animal cells?
Less
Membrane
Hypotonic Solution
Outside the cell
Less
Greater
Water moves into the cell, leading to swelling and bursting
Water moves into the central vacuole,
What happens to a plant cell?
10c. What is a hypertonic solution?
The concentration of dissolved substances is fluid than in the cytoplasm.
Inside the cell
Concentration of dissolved substances
Less
Concentration of water
What happens to an animal cells?
What happens to a plant cell?
Greater
Membrane
Hypertonic Solution
Outside the cell
Greater
Less
Water moves out of the cell, leading to shrinkage
Water moves out of the cell, pressure, & leading to
Osmosis
Please load the CyberEd Biology Course Title: The Plasma
Membrane and Cellular Transport. Complete Interactive Lessons # 3.
A review of osmosis in the cell.
Interactive
Lesson
Cellular Transport: Passive and Active Transport
Cellular Transport: Passive and Active Transport
Now load the CyberEd Biology Course Title: The Plasma Membrane
and Cellular Transport. View scenes 20 - 29 and complete the
exercise below.
Multimedia
Presentation
Examine passive and active transport as two mechanisms helping to
maintain cellular homeostasis.
Scene 20
1. In passive transport, what determines the direction of movement of small particles?
The direction of movement of particles in passive transport is determined by the concentration gradient
(diffusion) between the cytoplasm fluid.
Scenes 21 – 22
2. Why do the molecules in facilitated
diffusion need help moving across the
plasma membrane?
Likely, the molecules are too large to pass
unaided through the plasma membrane with
the concentration gradient; they need to
pass through special transport proteins.
3. Does facilitated diffusion require the cell
to expend energy to move substances?
Why or why not?
No, the molecules move by simple diffusion,
they just require a concentration gradient
and special transport proteins to help them
pass through the plasma membrane.
Scene 23
4. Fill in the table, identifying similarities and differences between passive transport and active transport.
What drives the movement of the
molecules across the plasma membrane?
Do the molecules move with or against
the concentration gradient?
What size are the molecules that are
moved across the plasma membrane?
Passive Transport
Active Transport
Concentration Gradient
ATP
With the gradient
Usually against the
gradient, but can be with it
Small for simple diffusion or
osmosis, larger for
facilitated diffusion
Any size
Scene 24
5. Recall that a cell needs to maintain homeostasis to perform its functions. If a cell has a higher
concentration of substances in the cytoplasm, which direction will water move? How can a cell continue
to maintain homeostasis if the concentration of water fluctuates?
Water will move into the cell. Active transport can be used to move water and other molecules into the
cell or out as needed.
Scene 25
6. Define endocytosis.
Scene 26
7. Describe the steps in endocytosis from the following
series of illustrations.
7a. Describe this step of endocytosis.
The plasma membrane begins engulfing particles from
7b. Describe this step of endocytosis.
The plasma membrane completely surrounds the
particles and pinches off into the cytoplasm to form a
vesicle, a plasma membrane enclosed sac with the
particles.
7c. Describe the final step of endocytosis.
The vesicle of digestive enzymes. The enzymes break
down the particles engulfed in the vesicles.
Scene 27
8. Sometimes cells receive messages from larger
molecules (like hormones). How might these larger
messenger molecules cross the plasma membrane?
How is this different from simple endocytosis?
Scene 28
9. Define exocytosis. What type of transport is exocytosis? Why might it be important for the cell to
carry out exocytosis?
The cell needs to remove waste products from the cytoplasm, but because they may be too large to
diffuse, or the concentration gradient is against the transport of the waste this function.
Scene 29
10. Fill in the summary table for particle transport across the plasma membrane.
Powered by
Examples
Passive Transport
Concentration
Gradient
Active Transport
ATP
Diffusion
Osmosis
Facilitated Diffusion
Facilitated Transport
In which direction do molecules
cross the plasma membrane?
Both
Both
Both
Both
Into the cell
Out of the cell
Active Transport
Please load the CyberEd Biology Course Title: The Plasma
Membrane and Cellular Transport. Complete Interactive Lessons # 2.
Examples of active transport in cells.
Interactive
Lesson
Active Transport
Please load the CyberEd Biology Course Title: The Plasma
Membrane and Cellular Transport. Complete Interactive Lessons # 4.
Interactive
Lesson
A review of the major mechanisms to move molecules across the
plasma membrane.
Comprehensive Exam: The Plasma Membrane and
Cellular Transport
Please take the computerized random CD-Rom exam provided by your
teacher.
Test