Transcript Cell Membrane

What do these pictures have in
common with each other?
Cell Membrane
• A thin nearly invisible
structure that surrounds
the cytoplasm of the
cell.
•Continuous membrane
that completely
surrounds the cell.
• Selectively permeable
Cell Membrane;
The Phospholipid Bilayer
Why do these phospholipids form this mirrored
double layer?
Hint…..the cell is made of about
80% water
Cell Membrane;
The Phospholipid Bilayer
Hydrophilic = Water loving
Phospholipid ‘head’
Hydrophobic = Water fearing
Phospholipid ‘tail’
Rank the molecules according to their
speed to cross the cell membrane from
fastest to slowest…..(or maybe not at all….)
Rank the molecules according to their
speed to cross the cell membrane from
fastest to slowest…..(or maybe not at all….)
Nonpolar
Polar
Glucose (too big
& polar)
Ions (have a
charge)
Cell Membrane
Fluid Mosaic Model
This currently accepted model was proposed by S.Singer &
G. Nicolson in 1972.
The phospholipids are the round yellow structures with the
blue tails,
The proteins are the blue lumpy structures that are scattered
around among the phospholipids.
cell_membrane_transport
Have you ever seen this before?
What type of art is this?
Fluid
On your paper, read the
descriptions of each part of the cell
membrane & label the diagram.
Carbohydrates
Phospholipids
Cholesterol
Cytoskeleton
Protein
Parts of Cell Membrane
Cell Membrane’s Parts
• Phospholipids
•Protein – helps regulate what passes through the
cell
•Cholesterol – provides strength in membrane
•Carbohydrates- act as source of protection &
recognition of other molecules
•Cytoskeleton- helps provide structure & shape to
cell
Cell Membrane’s Proteins
• Floating around in the cell membrane are different
kinds of proteins.
•They are not held in any fixed pattern but instead
float around in the phospholipid layer.
•Generally these proteins structurally fall into four
categories...
4 Types of Cellular Membrane Proteins
1.
Enzyme proteins catalyze many
chemical reactions
Ex. produces cell energy molecules
& perform photosynthesis in plants
Recognition proteins that identify
the cell to other cells
2. Ex. Immune system & blood types
3.
Transport / carrier proteins that
regulate molecules crossing the
membrane. Ex. Ions such as Na+ or K+
or larger molecules C6H12O6
4 Types of Cellular Membrane Proteins
Cell Signaling allows cells to signal.
4.
Insulin is the chemical signal that
operates gated channels found on the
surface of muscle and liver cells.
These gated channels are transport
proteins that allow for the inward
passage of sugar from the blood and
body fluids into a cell's cytoplasm.
The gated transport proteins are open
for sugar transport only when signaled
by the presence of insulin.
Lipid Rafts ?
• In artificial membranes, different lipids separate from each other based
on their physical properties, forming small islands called lipid rafts.
• These rafts have a higher concentration of certain specialized lipids and
are also distinguished by a different assortment of proteins. Certain
types of proteins cluster together in rafts, while others remain mostly
outside of rafts. The big question is, to what extent do these rafts, seen
readily in artificial membranes, actually exist in living cells?
• Using advanced laboratory methods and imaging techniques, some
researchers found evidence that rafts, indeed, do form in living cellular
membranes, but these rafts may be small and transitory. Although the
existence of lipid rafts in cellular membranes remains controversial,
many scientists believe they serve as communication hubs by recruiting
proteins that need to come together in order to transmit a signal.
Researchers are beginning to link
lipid rafts with a variety of diseases,
including AIDS, Alzheimer's, anthrax,
and atherosclerosis.
Red Blood Cells….
Some proteins on the RBC…….
Red Blood Cells….
The same thing applies
with Rh factors…
If a person is Rh positive,
then the person has Rh
antigens.
If a person is Rh negative,
then the person has NO
antigens, and then will
have Rh antibodies.