summary 1.cell doctrine; 2.two major types of microscopes: light and electron; 3.limitation of...
Post on 19-Dec-2015
218 Views
Preview:
TRANSCRIPT
Summary
1. Cell doctrine;2. Two major types of microscopes: light and electron;3. Limitation of resolution: wavelength of radiation;4. Advantage and disadvantage of light and electron MS5. Different types of light microscopes: bright field,
phase contrast, DIC, dark field,fluorescent, confocal6. Image processing: digital enhancement7. Two major types of EM: TEM and SEM 8. Additional tricks: shadowing, freeze-fracture, freeze
etching, negative staining, tomography;9. Live imaging, calcium indicators, caged compounds,
GFP, pulse chasing
Cell membrane: thin layer of dynamic and fluid lipid and protein molecules held together by noncovalent interactions
30% of the proteins encoded in our genome are membrane proteins
Diffuse across 2 um in 1 sec!
Needs phospholipidtranslocators
Properties of the lipid bilayerLiposome and black membranes
Cholesterol decreases permeability and fluidity at highConcentrations but also inhibits phase transition
“freeze” or “gel”
Lipid rafts are small, specialized areas in membraneswhere some lipids (primarily sphingolipids and cholesterol)
and proteins are concentrated
GPI-linked
70 nm in diameter
The asymmetrical distribution of phopholipids and glycolipids in the lipid bilayer
Phosphotidylcholine and sphingomyelin: outerPhosphotidylethanolamine and phosphotidylserine: inner
Negative inside
PKC requires phosphotidylserine
Apoptotic cells have their phosphotidylserine translocated to outer bilayer
Phosphotidylinositol--lipid kinases add phosphate groups in the inositol ring (PI3-kinase)Phospholipases cleave the inositol phospholipid molecules into twofragments
Glycolipids are only present on the outer monolayer
ProtectionElectrical effectsCell-recognitionEntry points for bacteria
No genetic evidence
Ganglioside:
Various ways membrane proteins associate withthe lipid bilayer
Glycosylphosphatidylinositol(GPI) and phosphatidylinositol-specific Phospholipase C (PIPC)
Some barrels form large transmembrane channels
10 aa is sufficient, barrels are rigidand hyropathy plots cannot identify barrels
Crystallize readily, abundant in outer membranes of mito, chloroplast and bacteria. Pore-forming proteins (porin). Loops of polypeptide chain in the lumen.Selective (maltoporin). Some are receptors or enzymes not transporters.
Membrane proteins can be solubilized and purified in detergentsamphipathic
Charged (ionic) -sodium dodecyl sulfate (SDS)Uncharged(nonionic) -Triton
Spectrin is a cytoskeletal protein noncovalently associatedwith the cytosolic side of the red blood cell membrane
Measuring the rate of lateral diffusion by photobleaching
Fluorescencerecovery afterphotobleaching
FluorescenceLoss inphotobleaching
Domains of an epithelial cell
Proteins and lipids are NOT always free to go anywhere they want
Intercellular junctions
The cell surface is coated with a carbohydrate layer
GlycoproteinsGlycolipidsSome proteoglycans
Ruthenium redLectins
Summary
1. Membranes are made of lipids and proteins;2. Lipid bilayer is a energetically favored structure;3. Fluidity, permeability and asymmetry of lipid bilayer4. Membrane proteins and transmembrane domains;5. Membrane protein modifications and asymmetry;6. RBCs are good models for plasma membrane;7. Membrane proteins in some membranes are more free to
move laterally;8. Carbohydrate layer.
top related