Catalyst
 1. What are the 3 parts of the Cell Theory?
The smallest…
All life is made…
All cells come…
2. What is the function of the:
 Cell membrane
 Ribosomes
 Cytoplasm
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
Coffee Filter Intro
2) Iodine bag set up
3)
Plasma Membrane Lecture
4) Oil/Water demo during notes
HW: plasma membrane coloring
1)
copyright cmassengale
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.
(inside of cell wall if present)
 Has three main jobs:
Separate cells from the
outside
2. Protect cells from the
environment
3. Decides what can enter
(or exit) the cell
1.
Selective permeability: the ability that
allows 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 nonpolar tails away
from water,
phospholipids
form a two-sided
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
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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
A
b) B
c) Both A and B
d) Neither A nor B
B
Question 3
Which part of the diagram below would
not mix well with water?
a) A
A
b) B
c) Both A and B
d) Neither A nor B
B
Question 4
Which part below will end up in the
middle of a bilayer?
a) A
A
b) B
c) Both A and B
d) Neither A nor B
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:
https://www.youtube.com/watch?v=Pfu1DE9PK2w
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.
Plasma Membrane Worksheet/Coloring