The Cell Membrane
AKA
The Plasma Membrane
AKA
The Lipid Bilayer
Some Electron Micrographs
Made up of two
layers of
phospholipids and
proteins with some
cholesterol
•
Basic Lipid Bilayer Structure
• Individual molecules not
bonded to one another –
held together by
hydrophilic and
hydrophobic ends of lipids
•Allows membrane to “flow”
– form vacuoles, divide, etc.
•Kinda like soap bubbles
Carbohydrate chains on the outside act
as identifiers often called Receptor
Molecules
Proteins form transport tubes and binding
sites. Binding sites are another form of
Receptor Molecule.
Different receptor molecules
have specific shapes
Receptor Molecule Functions
• Some of the proteins and carbohydrate
“trees” on the surface act as identifiers
• Allow immune cells to detect non-self and
abnormal cells
• Detects useful materials (“food”) in
environment for ingestion.
• Allows cells to coordinated functions – e.g.
neurotransmitters send nerve “signal”
(impulse) to next cell.
Transport Functions
• Moving material in and out of the cell
• Semipermeability = Some material diffuses
through membrane
• Semipermeability allows inside of cell to
be different from outside
• Other material is “pumped” through.
• Still other material can’t get through (or
“fools” the membrane into letting it in)
Main Function:
• Maintain the concentration of chemicals on the
inside of the cell
i.e. regulate the internal environment of the cell
• Affect which materials go in and/or out
But how??
“Get in there”
• Receptor Mediated Endocytosis –
Bringing large molecules or chunky bits
into the cell.
• Phagocytosis – Cellular “eating”
• Pinocytosis – Cell “drinking”
Animation