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.
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.
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.
