1. The Cell Membrane
FOS 3
Infectious Disease Unit

2. Composition of Cell
Membrane
 Cell Membranes are
NOT all identical, but
have FOUR common
parts:
 Lipid Bilayer
 Transmembrane Protein
 Network of supporting
fibers
 Glycoproteins
 On outside of cell
 Cell Surface has a
carbohydrate coat to
prevent sticking.

3. Lipid Foundation-
Phospholipid Bilayer
Consist of a:
Glycerol backbone
Fatty Acid tails
(nonpolar/
hydrophobic)
Phosphorylated
alcohol
(polar/hydrophilic)

4. Lipid Foundation-
Phospholipids
Fatty Acid side is
NONPOLAR
Nonsoluble in
water
Phophate side is
POLAR
Soluble in water

5. Lipid Bilayer
Creates barrier to
water soluble
molecules
Inside (tails) of
bilayer are nonpolar
and therefore
insoluble to water
Lipid bilayer is
fluid, yet stable.

6. Fluid Mosaic Model

7. If you want more information of this go to:http://www1.umn.edu/ships/9-
2/membrane.htm
History of the Fluid Mosaic Model

8. Controls the fluidity of the
Cell Membrane
Temperature
Length of tails and kinks in tails
Cholesterol

9. How do things get through if
there is a barrier?
Simple diffusion.
Through “kinks” in
the fatty acid tails
Closely aligned tails
have C-C (single
bonds)
C=C (double/triple
bonds) cause “kinks”

10. Transmembrane Proteins
extend across lipid bilayer
 These proteins can
have both a polar and a
nonpolar region.
 Enables them to be
embedded in the
nonpolar (hydrophobic)
area of the membrane
 Polar regions are
anchored in the water
 Provide CHANNELS into
the cell but only for
selected items.

11. Proteins act as Cell
Identification Markers
Lipids and proteins within the membrane
may have a carbohydrate chain attached
These glycolipids and glycoproteins often
function as cell ID markers, allowing cells to
identify other cells
This is particularly important in the immune
system where cells patrolling the body’s
tissues identify and destroy foreign invaders
such as bacteria or viruses.

12. Cell Surface Receptors
It’s shape fits signal
molecules, such as
hormones.
Receptors enable cells to
detect hormones and a
variety of other
chemicals in their
environment
The binding of a
molecule and a receptor
initiates a chemical
change within the cell.

13. Channel Proteins
In some cases the channel
proteins simply act as a
passive pore. Molecules
will randomly move
through the opening in
a process called
diffusion. This requires
no energy, molecules
move from an area of
high concentration to
an area of low
concentration.

14. Carrier Proteins
They do not extend
through the
membrane
They bond and
drag molecules
through the lipid
bilayer and release
them on the
opposite side.

15. Proteins used to attach
Cytoskeleton
Receptor proteins help to attach the
cytoskeleton inside the cell.

16. Cholesterol in Cell Membrane
The phospholipid
bilayer also contains
cholesterol
molecules. This
gives the layer
greater
strength, more
flexibility, less fluid
and less permeable
to ions and
monosaccharides.

17. Major Histocompatibility
Complex
Unique to every individual
Except identical twins
Consists of proteins that attach to exterior
cells and antigens
Allows T-Cells in the immune system to
recognize and attack foreign cells
Glycolipids also differentiate between
tissues of same individual
A, B, AB and O blood group markers.

18. Membrane Protein Functions

19. Membrane Protein Functions