PowerPoint Learning Quest
Biology 9
Unit 5: Cell Biology (Part 2)
Created by: Jeff Wolf and Mike Graff
Objectives: After completing this
Learning Quest the student will…
Describe the function of
a cell membrane.
Explain the step-by-step
process of cell transport.
Describe, in detail the
processes of selective
permeability, passive
transport, diffusion,
osmosis, facilitated
diffusion, passive
transport, and active
transport.
Directions
1.
2.
3.
4.
Follow the instructions in
the Anticipation Guide
found in this PowerPoint
Presentation.
Follow the instructions and
answer all questions found
in the Learning Guide.
Follow the instructions in
the Conclusion Guide.
ALL THREE GUIDES CAN BE
FOUND IN THIS LEARNING
POWERPOINT QUEST.
Anticipation Guide (Page 1)
The focus of this unit
will be on how cells
receive nutrition and
dispense of waste
through the very
complex cell membrane.
First let’s review the
function of the cell
membrane and how
molecules move into
and out of the cell via
the cell membrane.
Anticipation Guide (Page 2)
To understand the
constant movement
of molecules into
and out of the cell
through the cell
membrane one must
first understand two
concepts: selective
permeability and
diffusion.
Anticipation
Guide
(Page
3)
Selective permeability means that a
membrane allows some substances to
cross over more easily than others.
Selective permeable membranes such
as a cell membrane can “select” which
molecules it will allow into and out of
the cell and which molecules it will not
allow into and out of he cell. Much of
what can diffuse across the plasma
membrane is based upon the size and
chemical makeup of the molecule.
Transport proteins, found built into the
cell membrane assist in the movement
of molecules through passive and
active transport. The cell membrane
along with the transport proteins work
together to in a process called
diffusion.
An example of a transport protein.
Anticipation Guide (Page 4)
Diffusion is the tendency for molecules of a
substance to spread out into any available
space. Molecules are often wandering
randomly when energy called thermal motion
or heat is applied. However, a diffusion of a
population of molecules can be directional.
For example, look at the diagram (a) to the
right. Now imagine that a membrane
separating pure water from a solution a food
coloring dye mixed with water. We first must
assume that the membrane is permeable to
the dye molecules. Therefore, the membrane
will allow dye molecules through the
membrane in both directions. The dye
molecules will move into the other side of the
membrane until there is an equilibrium or an
equal mount of dye molecules on both sides of
the membrane. Don’t forget that
molecules are in a constant state of
motion.
Anticipation Guide (Page 5)
Simply put, a substance when it comes into contact with a
membrane will diffuse from an area that is more
concentrated to an area which is less concentrated. This
diffusion across a membrane is called a passive transport.
Next let us move onto the Learning Guide to find out the
specific operations of the cell membrane.
Learning Guide (Page 1)
As mentioned, in the Anticipation
Guide, throughout the thin layer
of the cell membrane are found
protein transports that assist in
the diffusion process. One type of
transport is known as passive
transport. This particular type of
transport is passive because the
cell does not used any energy in
order for the diffusion of
molecules to take place.
Although, the membrane does
not exhibit any energy during
passive transport, selective
permeability still takes place.
Learning Guide (Page 2)
The passive transport of water
molecules across a selectively
permeable membrane is called
osmosis.
As seen in the diagram to the left, the
membrane is permeable to water but
not to the solute. Therefore, the
water within the tube does not
transfer equally because the solution
to the left of the membrane is
hypotonic and the solution to the
right hypertonic.
Let us exam the difference between
these two types of solutions.
Learning Guide (Page 3)
A hypotonic solution is a
solution with a low solute
concentration and a high
water concentration.
A hypertonic solution has a
high solute concentration.
As seen in the diagram, the
hypotonic solution has a low
solute concentration and a
higher water concentration.
Thus, water will diffuse across
the membrane from the
hypotonic solution to the
hypertonic solution to
establish and equilibrium. This
is the process of osmosis.
Learning Guide (Page 4)
When a cell is said to have an equal
concentration of solute on both sides of the
cell membrane that solution is said to be
isotonic. Refer to page 77 – Figure 4.26
It is very important for a animal cell or plant
cell to balance water gain or loss.
When a cell balances the input and output of
water equally, it is said to have a Isotonic
solution (a).
When a cell has more water coming into
through the membrane than leaving this cell
has a hypotonic solution (b)
Finally, when a cell has more water leaving
through the membrane than coming into
through the cell membrane, this cell has a
hypertonic solution ( c ) .
Learning Guide (Page 5)
An example of an active transport
transferring molecules across the membrane
with the help of ATP
Cell membranes not only
have passive transports but
also has active transports, as
well.
Active transports require
energy from the cell in order
to move molecules across
the cell membrane. As seen
in the diagram to the right.
Active transports uses ATP,
produced by the cell’s
mitochondria, as an energy
source to transport
molecules across the
membrane.
Learning Guide (Page 6)
Over the past few slides
we have talked about
how small molecules
enter and leave the
animal or plant cell.
Next we will talk about
how larger molecules
are transported into or
out of your cells. This
can be accomplished by
two processes known
as either exocytosis or
endocytosis.
Learning Guide (Page 7)
When the cell needs to obtain or
release large molecules such as a
protein; they do this through a
process known as exocytosis or
endocytosis.
When the cell releases larger
molecules it packages them into
vesicles and moves them closer to the
membrane. When the vesicle comes in
contact with the cell membrane it
opens its container and releases the
molecule outside of the cell. This
process is known as exocytosis (a).
Learning Guide (Page 8)
When the cell needs
to take larger
molecules into the
cell, a vesicle is
formed around the
molecule. The
vesicle is then taken
into the cell through
a process called
endocytosis (b).
Conclusion Guide (Page 1)
a.
b.
The two types of
Endocytosis
include:
Pinocytosis – or
“cellular drinking”
where cells can gulp
droplets of fluid.
Phagocytosis – or
“cellular eating”
where a cell engulfs
a particle and
packages it within a
food vacuole
Conclusion Guide (Page 2)
Exocytosis and Endocytosis: The movement of large molecules
within your cells.
Work Cited
http://micro.magnet.fsu.edu/cells/animals/images/plasmamembrane.jpg
http://www.usd.edu/~bgoodman/realcell.JPG
http://www.cneccc.edu.hk/subjects/bio/album/Chapter4/images/PASSIVE_TRAN
SPORT.jpg
http://lhs.lps.org/staff/sputnam/Biology/U3Cell/endocytosis_1.png
After completing the test, move onto Unit #6.