Date post: | 16-Feb-2017 |
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Inner organization of the cellStructure
BarriersMaintenance of the inner structure of the cell
FunctionTransportSignal transmission
Unity of structure and functionMembrane structureMembrane transportCell compartmentalization and protein sortingVesicle transportSignal transmission
Structur & organization of the main components of biological membranes
Lipid bilayerMembrane proteins
Membrane lipids are amphipatic and form bilayers in watery milieu
Lipid bilayer behaves like a two dimensional liquid
2mm/s
Fluidity depends on the composition of the lipid bilayer
Fatty acidssaturatedunsaturated
Lipid compositionCholesterol Different phospholipidsGlycolipids
CholesterolA B
Stabilizes lipid bilayerPrevents transport of small water soluble moleculesSeparates CH-chains to prevent cristallisation
Phospholipids are two-dimensional solvents for membrane proteins
Lipid bilayer is assymetrical
Lipid bilayers are not permeable for solvents and ions
Membrane proteins have different functions
Structure of membrane proteinsAssociation with lipid-bilayer
Membrane proteins can be linked to lipid bilayer in different ways
Most transmembrane proteins span the lipid bilayer with an αlpha-helix
Transmembrane proteins can water-filled transmembrane channels
Hydrophilic side chains are directed towards the inner core of the pore which is formed by hydrphobic single chains
Maximisation of hydrogen bond formation through „beta-Barrel“
Example: Porines
16 beta-sheets form a transmembrane water-filled channel
Plasma membrane proteinsA B
GlycocalixProtectionSurface recognitionCell-Cell contacts
Cell-cell adhesion in blood
Membran proteins can be solved and purified with detergents
The plasma membrane is enforced by a cytoskeleton
Membrane proteins diffuse within the membrane
Fluorescence recoveryafter light bleaching
Cells can limit protein and lipid movement to certain membrane domains
Example: Epithelial cells