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Catalyst
 1. What are the 3 parts of the Cell Theory?
 2. What is the function of the:
 Cell membrane
 Ribosomes
 Cytoplasm
Cell Membrane Part 1
Today’s Objectives
SWBAT explain the purpose of the plasma
membrane and selective permeability.
SWBAT describe the structure of a
phospholipid.
SWBAT explain how the arrangement of
phospholipids lead to the formation of a
lipid bilayer
SWBAT identify the various components of
the plasma membrane
copyright cmassengale
Agenda
1)
2)
3)
4)
Coffee Filter Intro
Plasma Membrane Lecture
Oil/Water demo during notes
Construct the plasma membrane
HW: plasma membrane coloring
4
Homeostasis
Balanced internal condition of
cells
Also called equilibrium
Maintained by plasma or cell
membrane controlling what
enters & leaves the cell
5
Why do houses need walls?
Protect it from the
environment
Decide what can come in
and go out
Coffee Filter Demo
Plasma Membrane
 The plasma membrane
is the flexible outer layer
of cells.
 Has three main jobs:
1. Separate cells from
the outside
2. Protect cells from the
environment
3. Decides what can
enter or exit the cell
Selective permeability: the process of
allowing some molecules to pass into
the cell while keeping others out
>> Check for Understanding
How does a
window
screen show
selective
permeability?
What are membranes made of?
Membranes are made up of molecules
called phospholipids.
Phosphate
and
glycerol
What are membranes made of?
 Mixes
w/ water
“HATES”
water 
What are membranes made of?
To keep their
non-polar tails
away from
water,
phospholipids
form a twosided layer
called a bilayer.
Water
No Water
Water
Cell Membrane
Polar heads are hydrophilic “water loving”
Nonpolar tails are hydrophobic “water fearing”
Makes membrane “Selective” in what crosses
14
Oil and water
demo
Cell Membrane Part 2
What are membranes made of?
Guided Practice: A-B-C-D Cards
For each question, hold up the card
for whatever letter you think is
correct
Question 1
What term means that membranes
are made up of two back-to-back
layers?
a) selective permeability
b) non-polar tails
c) bilayer
d) phophate
Question 2
Which part of the diagram below is
polar?
a) A
b) B
c) Both A and B
d) Neither A nor B
A
B
Question 3
Which part of the diagram below
would not mix well with water?
a) A
b) B
c) Both A and B
d) Neither A nor B
A
B
Question 4
Which part below will end up in the
middle of a bilayer?
a) A
b) B
c) Both A and B
d) Neither A nor B
A
B
Question 5
In what types of organisms are cell
membranes found?
a) prokaryotes
b) eukaryotes
c) bacteria
d) all of the above
Question 6
Which of the following are
components of a phospholipid?
(hold up all that apply)
a) fatty acids
b) glycerol
c) monosaccharides
d) phosphate
Oil and Water Demo
What kinds of items do you think
will pass through?
For the items that can’t pass
through, what can we do to help
them get through?
Think and answer on your notes
1. In your own words, explain how a
pasta strainer shows “selective
permeability.” How is this similar to
cell membranes?
2. Why do phospholipids form
bilayers?
3. How does the oil and water demo
relate to the cell membrane?
Other Membrane Components
Turns out that the cell membrane is
NOT this simple:
Other Membrane Components
There are other parts to the
membrane, including cholesterol,
proteins, and carbohydrates
Cholesterol: Holding it Together
Cholesterol is mixed in with the phospholipids
to keep the tails from sticking together.
This gives the cells more stability
Transport Proteins: The Doors to the Cell
Some molecules have trouble crossing the
membrane… Why???
Transport proteins help molecules enter or exit
the cell.
Other Parts: Sending Signals
Other proteins and carbohydrates stick out
from the cell; they act as signals for other
cells to read.
The Fluid Mosaic Model
The parts of the cell membrane are not
held in place; they flow around the cell
like boats in water. This is called the
fluid mosaic model.
Exit Ticket
Homework
Plasma Membrane Worksheet/Coloring