membranes Flashcards
Membrane composition
lipids, protein and carbohydrates: lipids are covalently linked in branches by glycosidic bonds, cause dense matrix that protects cells.
Amphipathic meaning
both hydrophobic and hydrophilic regions e.g., polar head and hydrophobic tail
Phospholipid properties
2 fatty acid chains that are hydrophobic, can be saturated (straight) or unsaturated with a cis double bond (kink). Phosphate group is negatively charged Phosphotydl serine is the only charged phospholipid (-ve)
Cholesterol properties and use in membranes
Small polar head, rigid steroid ring, short linear non polar hydrocarbon chain. small can squeeze between lipids. Prevents rigidity, keeps fluid.
What are Phosphoinositides?
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell’s life and death. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes.
Micelle??
Micelles are formed in aqueous solution whereby the polar region faces the outside surface of the micelle and the nonpolar region forms the core. Micelles can deliver both hydrophilic and hydrophobic agents. Such structures can deliver macromolecules because these molecules can provide sustained and controlled release of macromolecules, provide chemical and physical stability of the encapsulated molecules, improve drug pharmacokinetics and favorable tissue distribution, and improve drug bioavailability
Liposomes??
A form of lipid, used to mimic membrane environments. Used to deliver drugs, to genetically modify as used as vectors and in cosmetics.
3 membrane characteristics?
fluid, flexible, self repairing
Fluidity in membranes?
individual phospholipids rotate on own axis or exchange in lateral plane.
If lots of saturated c-h chains tightly packed , no gaps, less fluid, but if unsaturated, more gaps, more fluid
Shorter chains mean more fluid
Adapt to temperature by ensuring membrane fluid at that temperature
cholesterol intercalate between, the more there is the more rigid in areas and spaces out phospholipids
FRAP?
fluorescent tag proteins in membrane (GFP) , zap with laser beam, loose fluorescence. Measure rate at which area after being bleached then recovered. Tells you how freely mobile protein in membrane is.
Integral membrane proteins ??
embedded, come parts in hydrophobic environment, heave and extra and intra cellular domain. Can be multipass
Tetrasponsins: only in one leaflet of membrane
Beta barrels: bacterial transporters and receptors (porins). beta barrels are more rigid
Peripheral protein?
associated with the membrane not embedded. Post translational modification adds lipids of fatty acid to anchor.
Are easier to extract
Can also be associated with other proteins
Ras is only active when associated with the membranes.
Hydropathy?
Hydropathy plots allow for the visualization of hydrophobicity over the length of a peptide sequence. A hydropathy scale which is based on the hydrophobic and hydrophilic properties of the 20 amino acids is used.
The intracellular domain need the amino acids to be able to survive in hydrophobic environment
Rafts?
Rigid structure in membrane where cholesterol and sphingolipids are. Makes membrane thicker. Are specialised areas where signalling occurs. called MICRODOMAINS. are dynamic as can form and disassemble
Detergents?
Slobs the membrane. Amphipathic and can displace phospholipids and create a micelle. Used to extract membrane proteins.
SDS is a detergent used
