Membrane Structure Flashcards
Funktion of the plasma Membran
Act as a barriers Prevent the contents of the cell from escaping and mixing the surrounding medium Involved in cell communication Import export Cell growth and motility
Internal membrane
Form many different compartments in a eukaryotic cell
Lipid bilayer
Provides the basic structure for all cell membranes
The proteins on the Membran make the difference between the cells every cell have their one proteins which their functions
The main phospholipid
Phosphoglycerin
Phosphatidylglycerid
Phosphatidserin
Phosphatidylcholine
Phosphatidylinositol
Phosphatidyletanolamine
The hydrophobic effect
Drives structural rearrangement of lipid
Sealed compartment
A phospholipid bilayer spontaneously close to form a sealed compartment
Use the lowest energy
Liposomes
Are bilayer made in the form of spherical vesicles
Types of the movement that phospholipid molecules undergo
Flexion
Rotation
Lateral diffusion
Flip-flop (rarely occurs)
Move in their own mono layers
Lipid molecules do not move spontaneously from one monolayer to the other
Their are saturated and unsaturated tails … more short and unsaturated tails make the lipid layer more comfortable
Cholesterol a sterol
Is found in large amount in eukaryotic plasma membranes
They control the movement of the lipid layer
Membran Orientation
They retain their orientation during transfer between cell compartments
(Golgi-vesicles-membrane)
Lipid asymmetrically
Phospholipid and glycolipid are distributed asymmetrical in the lipid bilayer
Lipid asymmetry is functionally important in order to convert extracellular signals in intracellular ones
One function of Glikolipids is that they work as receptors, they catch the signals and give them into the intracellular space
Plasma membrane proteins Funktions
They have variety of funktions
Transporters and Channel (Na Pumps)
Anchors (intergrins)
Receptors (PDGF)
Enzymes(adenyl-cyclase)
Association between membrane protein and lipid bilayer
- Trans membran
- Monolayer associated alpha helix
- Lipid linked
- Protein-attachend
Trans membrane
Across the bilayer as a single alpha helix
Hydrophobic region interior of the bilayer
Hydrophilic region are exposed to the aqueous environment
Monolayer associated alpha helix
Located almost entirely in the cytosol and are associated with the cytosolic half of the lipid bilayer by an amphipathic alpha helix
Lipid linked
Lie entirely outside the bilayer on one side or the other, attached to the membrane only by one or more covalently attached lipid group
Protein attached
They are bound indirectly to one or the other face of the membrane, held in place only by their interactions with other membrane proteins
Most trans membrane protein
In most transmembrane protein the polypeptide chain crosses the lipid bilayer in a alpha helix conformation
Single pass transmembrane protein
Multi pass transmembrane protein
Transmembrane hydrophilic pore
Can be formed by multiple amphipathic alpha helicas
Beta sheets
Rolled up beta sheets (beta barrels)
Form large and rigid transmembrane channel
They carriers molecules that are water soluble
Solubilize of Membran proteins
Membran proteins can be solubilized with a mild non ionic detergent
The hydrophobic part of detergent hint on the hydrophobic part of the protein or lipid
Cell cortex
The plasma Membran is reinforced by underlying cell cortex
Under the plasma Membran are fiber proteins (cell cortex)
Exp. By erythrocytes they are dimerik protein spektrin
Cortical cytoskeleton
Gives membranes mechanical strength and restricts Membran protein diffusion
Give erythrocytes to cross a very thin kapillar and have take their structure
Fluorescence recovery after photobleaching
With FRAP the rate of lateral diffusion of a Membran protein can be measured
Restriction of lateral mobility of specific plasma membran protein
- Self assemble into large aggregates
- Tethered by interaction with assemblies of macromal (outside the cell)
- Tethered by interaction with assemblies of macromal (inside the cell)
- Interact with proteins on the surface of another cell (epithelial cells in the gut)
Glycosyated
Many Membran protein are glycosyated
Glikoprotein (short saccarid chain)
Proteoglikan(one or more long chain
Together build a glikokaliks
Cells with glikokaliks have a lot of functions
For example: to know infection regions
