Transcript The Cell Membrane

The Cell Membrane
Animal Cell
Plant Cell
Prokaryotic Cell: Bacteria
Important Facts
 Lipid bi-layer
 Embedded proteins
 Encloses the cytoplasm
 Organelles and Cytosol (liquid)
 Separates inside of cell from outside
environment
 Semi-Permeable
 Controls what enters and leaves the cell
 Allows some things in and keeps others out
 Also known as “plasma membrane”
Cell Membrane Structure
 Fluid-like structure
 Not stiff or rigid
 Phospholipids and proteins can
drift/move around
 Proteins form patterns that look like a
mosaic
 Fluid Mosaic Model
 Current description for the membrane
Cell Membrane Structure
Cell Membrane Structure
 Bi-layer made up
of lipids and
proteins
 Phospholipids
 Special lipids
made of one
glycerol, two
fatty-acids and
a phosphate
Phospholipid Structure
Phospholipid Structure
Properties of Water Review
+
+
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 Water is a polar molecule
 Partially positively charged
(hydrogen)
 Partially negatively
charged (oxygen)
 Water molecules are
attracted to other
molecules
So polar molecules stick together and
repel away non-polar molecules
Properties of Water Review
Since water is
a polar
molecule the
opposite
charges on
other molecules
help them stick
together!!
Phospholipid Structure
 “Polar Heads”
 Hydrophilic
 “water loving”
 Phosphate part is
attracted to water
 Polar heads point to
watery parts of the
cell
 Cytoplasm
 Outside Environment
Phospholipid Structure
 “Non-Polar Tails”
 Hydrophobic
 Doesn’t like water
 Fatty-acids (lipid)
repels water
 Non-Polar tails point
towards each other
in the center of the
membrane
 Between the two
layers
Bi-Layer Arrangement
 The cytoplasm of the cell is an “aqueous” or
“watery” environment.
 How do the phospholipids arrange
themselves?
Remember….hydrophilic
and hydrophobic
areas.
Bi-Layer Arrangement
Hydrophilic
Hydrophobic
Bi-Layer Arrangement
Hydrophilic
Hydrophobic
Membrane Proteins
 Transmembrane Proteins
 Embedded in the cell membrane
 Exposed to both the inside and outside of the cell
 Peripheral Proteins
 Attached to the external or internal surface of the
membrane
 Channel Proteins
 Help move materials into and out of the cell
 Cell Markers
 Carbohydrate chains that identify cell types
 Enzymes
 Assist in chemical reactions
 Speed up and lower activation energy
Membrane Proteins
Cell Marker
Protein
Channel
Protein
Peripheral
Protein
Transmembrane
Protein
Figure 7-12 The Structure of the
Cell Membrane
The Cell Membrane
Section 7-3
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer