What is the cell membrane?
 AKA: Plasma membrane
 The boundary between the cell and the
environment
 Does every cell have a cell membrane?
 Yes!, Each and every cell has a cell membrane.
How do cell membranes help to maintain
homeostasis?
 The cell membrane allows nutrients to come into the
cell

Glucose, amino acids, lipids
 The cell membrane removes waste
Selective Permeability
 The cell membrane lets some molecules in and keeps
others out
 EX. A cell is low on glucose so the membrane lets
in some glucose, but does not overfill the cell with
the monomer.
Structure of the cell membrane
 What does the cell membrane look like up close?
Lets look at one
of these
structures up
close
Structure of cell membrane
 Phospholipids
 Phosphate head
 Glycerol
 2 Fatty acid tails
Phospholipids
 1.) Phosphate Head



Polar
Hydrophilic
Make up the outer borders of the
membrane
 2.) Fatty Acid Tails



Nonpolar
Hydrophobic
Make up the inner part of the
membrane
Structure of cell membrane
 Phospholipid bilayer
 2 layers of phospholipids make up a cell membrane
Phospholipid Bilayer
 Remember polar heads and nonpolar tails
The Fluid Mosaic Model of the cell
membrane
 Lipid bilayer is not strong & firm like a hard
shell, but it is fluid like a soap bubble
consistency
 So, it is called the Fluid Mosaic Model
(fluid like, with many proteins stuck in it)
The Fluid Mosaic Model of the cell
membrane
 It is a flexible membrane, made fluid
because of cholesterol molecules
located in the phospholipid bilayer.
 Proteins in the membrane move
around.
Other components of the cell membrane
 Cholesterol
 Helps to stabilize
the phospholipids
and keep them
from sticking
together
Other components of the cell membrane
 Carbohydrates- linked to lipids or
proteins
 Recognition of Cells – “Name tag of cell”
 Ex. Is the cell a heart cell, liver cell, or
brain cell?
 Ex. Glycolipids & Glycoproteins
(marker protein)
Other components of the cell membrane
 Proteins- make up 50 %- 70% of membrane
 Regulate which molecules enter and which
molecules leave a cell.
 Receive info & ID the cell
Types of proteins in the cell membrane
 Carrier Protein
 Allow needed substances or
waste materials to move
through the cell membrane
Types of proteins in the cell membrane
 Receptor Protein
 These have binding sites for molecules such as hormones or
substrates to bind to that can cause a chemical rxn in the cell
Types of proteins in the cell membrane
 Channel or Pore protein
 Hydrophilic channel – allows lipid insoluble
substances to pass in and out of cell.
Types of proteins in the cell membrane
 Glycoproteins
 Protein with what macromolecule attached to it?

Carbohydrate
 Functions for cell to cell recognition
Where are proteins located in the cell
membrane?
 Integral Proteins
 Proteins inside the cell membrane
 Peripheral Proteins
 Proteins outside the cell membrane
Lets build a cell membrane together
 http://www.wisc-
online.com/objects/index_tj.asp?objid=AP1101
 Cell membrane animation
Cell membranes help maintain homeostasis, what
is that?
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uc
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3.
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ai
2.
...
25% 25% 25% 25%
Cells breathing
Cells getting blood to
them
Cells maintaining
internal conditions
Cells reproducing
1.
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Where would you expect to find water in this cell
membrane?
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H
H
er
e
2.
50%
er
e
50%
Here
Here
1.
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When something is hydrophilic, it…
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al
..
m
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a
as
H
H
as
a
ch
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ic
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..
.
2.
50%
.
50%
Has a chemical
makeup that likes to be
around water
Has a chemical
makeup that does not
like to be around water
1.
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This picture shows what type of protein?
R
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C
ar
rie
ly
c
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2.
Receptor Protein
Channel Protein
Glycoprotein
Carrier Protein
ro
te
...
1.
...
25% 25% 25% 25%
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Identify the structure marked on the cell membrane:
le
s
ho
ec
7.
R
6.
lip
id
5.
C
4.
ph
o
3.
os
2.
Phospholipid
Cholesterol
Receptor protein
Channel protein
Glycoprotein
Carrier protein
Nucleic acid
Ph
1.
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te
ep
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to
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le
ic
ac
id
14% 14% 14% 14% 14% 14% 14%
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Identify the structure marked on the cell membrane:
le
s
ho
ec
7.
R
6.
lip
id
5.
C
4.
ph
o
3.
os
2.
Phospholipid
Cholesterol
Receptor protein
Channel protein
Glycoprotein
Carrier protein
Nucleic acid
Ph
1.
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te
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.
le
ic
ac
id
14% 14% 14% 14% 14% 14% 14%
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Identify the structure marked on the cell membrane:
le
s
ho
ec
7.
R
6.
lip
id
5.
C
4.
ph
o
3.
os
2.
Phospholipid
Cholesterol
Receptor protein
Channel protein
Glycoprotein
Carrier protein
Nucleic acid
Ph
1.
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te
ep
ro
to
l
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p
ha
ro
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nn
...
el
pr
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.
le
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ac
id
14% 14% 14% 14% 14% 14% 14%
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Identify the structure marked on the cell membrane:
50%
Pe
In
te
g
rip
he
ra
l
ra
l
Pr
o.
..
2.
Peripheral Protein
Integral Protein
Pr
ot
e.
..
1.
50%
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