Membrane Flashcards
Outer boundary of membrane size
5-10 nm
How we can see the membrane?
Too small therefore inly can be seen by electron microscopes
Bilayers stabilized by
Van der waals interactions in the fatty acyl chains
Polar head stabilize by
Ionic and HB bonds of polar heads with each other and with water
Plasma membrane components
1-lilid bilayer
2- proteins — individual and complex proteins— penetrate and extend out
Lipid bilayer fluid or rigid?
Fluid
Plasma membrane vs internal membrane
Plasma: outer boundary of cell
Internal: enclosed compartments (organelles)
Cell membrane functions
-compartmentalization
-framework
-selective permeability
-solute transport
-response to external stimulus
-cell-cell communication
-energy transduction
Lipid to protein ratio depends on
1- type of cellular membrane
2- type of organisms
3- type of cell
Lipid kinds in membrane
1- phosphoglycerides
2- sphingolipids
3- cholesterol
Phosphoglyceride
2 fatty acids (1 saturated-1 unsaturated)
1 glycerol
1 phosphate
Most have small hydrophilic group linked to phosphate
- amphipathic
- kinds:
1- phosphatidylethanolamine
2- phosphatidylserinr
3- phosphatidylcholine
Phosphatidylserine
Net negative charge
Sphingolipids
Derivative ceramide
Carbohydrates are added — glycolipid
Multiple sugars added — ganglioside
Glycolipids
Exclusively on exoplasmic face
Have glycolipids with glycerol back bine but we mean glycosphingolipids
Where glycolipids are made
Lumen of golgi (consider equivalent to outside of cell)
Exocytosis and add to exoplasmic face
Sterols
50% of membrane
Most important: cholesterol (amphipathic)
Membrane folding
Unfavorable planar position
Fold spontaneously—> lipososomes
Membranes are always continuous-hydrophobic tail doesn’t like water
Phophatidylserine
Protein requires them on cytosolic face
During apoptosis move to exoplasmic face and signal neighbors
Plasma membrane contains:
(2-10)% carbohydrates
90% glycoproteins
10% glycolipids
Mebrane carbohydrates
Face to exoplasmic face
Addition carbohydrate to protein
Glycosylation
Most complex post transitional modification
Membrane proteins
1- integral (pass through)
2- peripheral (non-covalently bind to either sides)
3- lipid-anchored proteins (covalently bind to lipid membranes)
Integral proteins function
1- transporters
2- anchors
3- receptor
4- electron transporter
Integral protein
- amphipatic
- hard to isolate in soluble form
- glycophorin A: major erythrocyte plasma membrane
Transmembrane domains: 20 non-polar aAA as alpha helix span in lipid bilayer - positively charged arg and lys near cytosolic face anchor the protein
