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Membrane lectures (lipid bilayer (general information (5nm thick (50A°…

- - - - possible for groups of membrane proteins to assemble at particular sites within the membranes
    - - temperature
      - cholesterol
      - saturation of acyl chains
      - length of acyl chains
  - - - phosphatidylinositol
      - phosphatidylserine
      - phosphatidylethanalamine
    - - glycolipid
      - phosphatidylcholine
      - sphingomyelin
  - - - energetically unfavorable as polar molecule must move through hydrophobic environment
  - - - 50A° total
      - 30A° for just hydrophobic tails
  - - - cholesterol contributes to overall stability of phospholipid bilayer
    - - sphingolipids
      - glycerophospholipids
  - - - ions
      - larger uncharged polar molecules
        
        glucose
        
        amino acids
        
        nucleotides
    - - small uncharged polar molecules
        
        glycerol
        
        ethanol
        
        H20
      - small hydrophobic molecules
        
        benzene
        
        Co2
        
        o2
- - - - still energetically unfavourable --> how is this problem overcome?
        
        hydrogen bonding between the partial negative charge in the carbonyl oxygen and the partial positive charge in the amide nitrogen
    - - transporters
        
        2 classes
        
        carrier proteins
        
        general information
        
        specific solute binding sites
        
        switch between different conformations which are open to the 2 sides of the membrane (alternative access mode)
        
        no continuous channel between 2 sides
        
        required to transport nearly all small organic molecules
        
        amino acids
        
        sugars
        
        nucleotides
        
        Energy consideration
        
        passive transport
        
        molecules move with gradient and stop when concentrations have been equilibriated
        
        need for flip flop
        
        molecules move accross membrane without expenditure of energy
        
        active transport
        
        secondary active transport system
        
        1 more item...
        
        use of energy to drive molecules against gradient
        
        2 types
        
        coupled transport
        
        antiport : oppositie direction
        
        uniport
        
        carries one unique molecule
        
        channel proteins
        
        ion selective
        
        =/= ion pump
        
        open
        
        continuous channel through which ions can pass
        
        closd
        
        gating
        
        ligand gated : response to binding of ligand
        
        mechanical gated in auditory cells response
        
        voltage gating: response to voltage differences accross membranes
        
        stimulus causes sufficient depolarisation of plasma membrane causes voltage gated NA+ channels to open
        
        2 more items...
- - - - insulin receptor
        
        binding to receptor activates tyrosine kinase addition of phophates to tyrosine residues of proteins